RetroSearch Browse

Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://smithsonian.github.io/SuperNOVAS/apidoc/html/novas_8h.html below:

SuperNOVAS: include/novas.h File Reference

#define ASEC2RAD   (DEG2RAD / 3600.0) [rad/arcsec] 1 arcsecond in radians
#define ASEC360   (360 * 60 * 60) [arcsec] Number of arcseconds in 360 degrees.
#define BARYC   NOVAS_BARYCENTER #define CAT_ENTRY_INIT   { {'\0'}, {'\0'}, 0L, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 } #define DE405_AU   1.4959787069098932e+11 #define DEFAULT_CIO_LOCATOR_FILE   "/usr/share/novas/cio_ra.bin" #define DEFAULT_GRAV_BODIES_FULL_ACCURACY   ( DEFAULT_GRAV_BODIES_REDUCED_ACCURACY | (1 << NOVAS_JUPITER) | (1 << NOVAS_SATURN) ) #define DEFAULT_GRAV_BODIES_REDUCED_ACCURACY   ( (1 << NOVAS_SUN) ) #define DEG2RAD   (M_PI / 180.0) [rad/deg] 1 degree in radians
#define HELIOC   NOVAS_HELIOCENTER #define IN_SPACE_INIT   {{0.0}, {0.0}} #define M_PI   3.14159265358979323846 Definition of π in case it's not defined in math.h.
#define NOVAS_ARCMIN   (NOVAS_DEGREE / 60.0) [rad] An arc minute expressed in radians.
#define NOVAS_ARCSEC   (NOVAS_ARCMIN / 60.0) [rad] An arc second expressed in radians.
#define NOVAS_AU   1.495978707e+11 #define NOVAS_AU_KM   ( 1e-3 * NOVAS_AU ) [km] Astronomical Unit (AU) in kilometers.
#define NOVAS_AU_SEC   ( NOVAS_AU / NOVAS_C ) [s] Light-time for one astronomical unit (AU) in seconds.
#define NOVAS_C   299792458.0 [m/s] Speed of light in meters/second is a defining physical constant.
#define NOVAS_C_AU_PER_DAY   ( NOVAS_DAY / AU_SEC ) [AU/day] Speed of light in units of AU/day.
#define NOVAS_CIO_CACHE_SIZE   1024 [pts] cache size for GCRS CIO locator data (16 bytes per point).
#define NOVAS_DAY   86400.0 [s] The length of a synodic day, that is 24 hours exactly.
#define NOVAS_DEFAULT_WAVELENGTH   0.55 #define NOVAS_DEGREE   (M_PI / 180.0) [rad] A degree expressed in radians.
#define NOVAS_DELAUNAY_ARGS_INIT   { 0.0, 0.0, 0.0, 0.0, 0.0 } #define NOVAS_EARTH_ANGVEL   7.2921150e-5 [rad/s] Rotational angular velocity of Earth from IERS Conventions (2003).
#define NOVAS_EARTH_FLATTENING   (1.0 / 298.25642) Earth ellipsoid flattening from IERS Conventions (2003). Value is 1 / 298.25642.
#define NOVAS_EARTH_INIT   NOVAS_PLANET_INIT(NOVAS_EARTH, "Earth") #define NOVAS_EARTH_RADIUS   6378136.6 [m] Radius of Earth in meters from IERS Conventions (2003).
#define NOVAS_EMB_INIT   NOVAS_PLANET_INIT(NOVAS_EMB, "EMB") #define NOVAS_EQUATOR_TYPES   (NOVAS_GCRS_EQUATOR + 1) #define NOVAS_FRAME_INIT #define NOVAS_G_EARTH   3.98600433e+14 [m³/s²] Geocentric gravitational constant, from DE-405.
#define NOVAS_G_SUN   1.32712440017987e+20 [m³/s²] Heliocentric gravitational constant, from DE-405.
#define NOVAS_GPS_TO_TAI   19.0 [s] TAI - GPS time offset
#define NOVAS_HOURANGLE   (M_PI / 12.0) [rad] An hour of angle expressed in radians.
#define NOVAS_JD_B1900   15019.81352 [day] Julian date at B1900
#define NOVAS_JD_B1950   2433282.42345905 [day] Julian date at B1950
#define NOVAS_JD_HIP   2448349.0625 [day] Julian date for J1991.25, which the Hipparcos catalog is referred to.
#define NOVAS_JD_J2000   2451545.0 [day] Julian date at J2000
#define NOVAS_JD_MJD0   2400000.5 [day] Julian date at which the Modified Julian Date (MJD) is zero
#define NOVAS_JD_START_GREGORIAN   2299160.5 #define NOVAS_JUPITER_INIT   NOVAS_PLANET_INIT(NOVAS_JUPITER, "Jupiter") #define NOVAS_KM   1000.0 [m] A kilometer (km) in meters.
#define NOVAS_KMS   (NOVAS_KM) [m] One km/s in m/s.
#define NOVAS_MAJOR_VERSION   3 Major version of NOVAS on which this library is based.
#define NOVAS_MARS_INIT   NOVAS_PLANET_INIT(NOVAS_MERCURY, "Mars") #define NOVAS_MATRIX_IDENTITY   {{{1.0, 0.0, 0.0}, {0.0, 1.0, 0.0}, {0.0, 0.0, 1.0}}} #define NOVAS_MATRIX_INIT   {{{0.0}}} #define NOVAS_MERCURY_INIT   NOVAS_PLANET_INIT(NOVAS_MERCURY, "Mercury") #define NOVAS_MINOR_VERSION   1 Minor version of NOVAS on which this library is based.
#define NOVAS_MOON_INIT   NOVAS_PLANET_INIT(NOVAS_MOON, "Moon") #define NOVAS_NEPTUNE_INIT   NOVAS_PLANET_INIT(NOVAS_NEPTUNE, "Neptune") #define NOVAS_OBJECT_INIT   { -1, 0L, {'\0'}, CAT_ENTRY_INIT, NOVAS_ORBIT_INIT } #define NOVAS_OBJECT_TYPES   (NOVAS_ORBITAL_OBJECT + 1) #define NOVAS_OBSERVABLE_INIT   { 0.0, 0.0, 0.0, 0.0 } #define NOVAS_OBSERVER_PLACES   (NOVAS_SOLAR_SYSTEM_OBSERVER + 1) #define NOVAS_ORBIT_INIT   { NOVAS_ORBITAL_SYSTEM_INIT, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 } #define NOVAS_ORBITAL_SYSTEM_INIT   { NOVAS_SUN, NOVAS_ECLIPTIC_PLANE, NOVAS_GCRS, 0.0, 0.0 } #define NOVAS_ORIGIN_TYPES   (NOVAS_HELIOCENTER + 1) #define NOVAS_PLANET_BUNDLE_INIT   { 0, {{0.0}}, {{0.0}} } #define NOVAS_PLANET_GRAV_Z_INIT #define NOVAS_PLANET_INIT(num, name)   { NOVAS_PLANET, num, name, CAT_ENTRY_INIT, NOVAS_ORBIT_INIT } #define NOVAS_PLANET_NAMES_INIT #define NOVAS_PLANETS   (NOVAS_PLUTO_BARYCENTER + 1) #define NOVAS_PLUTO_BARYCENTER_INIT   NOVAS_PLANET_INIT(NOVAS_PLUTO_BARYCENTER, "Pluto-Barycenter") #define NOVAS_PLUTO_INIT   NOVAS_PLANET_INIT(NOVAS_PLUTO, "Pluto") #define NOVAS_REFERENCE_SYSTEMS   (NOVAS_ITRS + 1) #define NOVAS_REFRACTION_MODELS   (NOVAS_WAVE_REFRACTION + 1) #define NOVAS_RMASS_INIT #define NOVAS_SATURN_INIT   NOVAS_PLANET_INIT(NOVAS_SATURN, "Saturn") #define NOVAS_SOLAR_CONSTANT   1367.0 #define NOVAS_SOLAR_RADIUS   696340000.0 #define NOVAS_SSB_INIT   NOVAS_PLANET_INIT(NOVAS_SSB, "SSB") #define NOVAS_SUN_INIT   NOVAS_PLANET_INIT(NOVAS_SUN, "Sun") #define NOVAS_SYSTEM_B1950   "B1950" #define NOVAS_SYSTEM_FK4   "FK4" #define NOVAS_SYSTEM_FK5   "FK5" #define NOVAS_SYSTEM_HIP   "HIP" #define NOVAS_SYSTEM_ICRS   "ICRS" #define NOVAS_SYSTEM_J2000   "J2000" #define NOVAS_TAI_TO_TT   32.184 [s] TT - TAI time offset
#define NOVAS_TIMESCALES   (NOVAS_UT1 + 1) #define NOVAS_TIMESPEC_INIT   { 0, 0.0, 0.0, 0.0, 0.0 } #define NOVAS_TRACK_INIT   { NOVAS_TIMESPEC_INIT, NOVAS_OBSERVABLE_INIT, NOVAS_OBSERVABLE_INIT, NOVAS_OBSERVABLE_INIT } #define NOVAS_TRANSFORM_INIT   { -1, -1, NOVAS_FRAME_INIT, NOVAS_MATRIX_INIT } #define NOVAS_TRANSFORM_TYPES   (ICRS_TO_J2000 + 1) #define NOVAS_URANUS_INIT   NOVAS_PLANET_INIT(NOVAS_URANUS, "Uranus") #define NOVAS_VENUS_INIT   NOVAS_PLANET_INIT(NOVAS_VENUS, "Venus") #define NOVAS_VERSION_STRING   #NOVAS_MAJOR_VERSION "." NOVAS_MINOR_VERSION The version string of the upstream NOVAS library on which this library is based.
#define NOVAS_WOBBLE_DIRECTIONS   (WOBBLE_PEF_TO_ITRS + 1) #define OBSERVER_INIT   { NOVAS_OBSERVER_AT_GEOCENTER, ON_SURFACE_INIT, IN_SPACE_INIT } #define ON_SURFACE_INIT   { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 } #define ON_SURFACE_LOC(lon, lat, alt)   { lon, lat, alt, 0.0, 0.0, 0.0 } #define RAD2DEG   (1.0 / DEG2RAD) [deg/rad] 1 radian in degrees
#define SIZE_OF_CAT_NAME   6 Maximum bytes in catalog IDs including string termination.
#define SIZE_OF_OBJ_NAME   50 Maximum bytes in object names including string termination.
#define SKY_POS_INIT   { {0.0}, 0.0, 0.0, 0.0, 0.0 } #define SUPERNOVAS_MAJOR_VERSION   1 API major version.
#define SUPERNOVAS_MINOR_VERSION   4 API minor version.
#define SUPERNOVAS_PATCHLEVEL   1 Integer sub version of the release.
#define SUPERNOVAS_RELEASE_STRING   "-devel" Additional release information in version, e.g. "-1", or "-rc1", or empty string "" for releases.
#define SUPERNOVAS_VERSION_STRING #define TWOPI   (2.0 * M_PI) 2π
enum novas_accuracy { NOVAS_FULL_ACCURACY = 0 , NOVAS_REDUCED_ACCURACY } enum novas_calendar_type { NOVAS_ROMAN_CALENDAR = -1 , NOVAS_ASTRONOMICAL_CALENDAR , NOVAS_GREGORIAN_CALENDAR } enum novas_cio_location_type { CIO_VS_GCRS = 1 , CIO_VS_EQUINOX } enum novas_date_format { NOVAS_YMD = 0 , NOVAS_DMY , NOVAS_MDY } enum novas_debug_mode { NOVAS_DEBUG_OFF = 0 , NOVAS_DEBUG_ON , NOVAS_DEBUG_EXTRA } enum novas_dynamical_type { NOVAS_DYNAMICAL_MOD = 0 , NOVAS_DYNAMICAL_TOD , NOVAS_DYNAMICAL_CIRS } enum novas_earth_rotation_measure { EROT_ERA = 0 , EROT_GST } enum novas_equator_type { NOVAS_MEAN_EQUATOR = 0 , NOVAS_TRUE_EQUATOR , NOVAS_GCRS_EQUATOR } enum novas_equatorial_class { NOVAS_REFERENCE_CLASS = 0 , NOVAS_DYNAMICAL_CLASS } enum novas_equinox_type { NOVAS_MEAN_EQUINOX = 0 , NOVAS_TRUE_EQUINOX } enum novas_frametie_direction { J2000_TO_ICRS = -1 , ICRS_TO_J2000 } enum novas_nutation_direction { NUTATE_TRUE_TO_MEAN = -1 , NUTATE_MEAN_TO_TRUE } enum novas_object_type { NOVAS_PLANET = 0 , NOVAS_EPHEM_OBJECT , NOVAS_CATALOG_OBJECT , NOVAS_ORBITAL_OBJECT } enum novas_observer_place {
  NOVAS_OBSERVER_AT_GEOCENTER = 0 , NOVAS_OBSERVER_ON_EARTH , NOVAS_OBSERVER_IN_EARTH_ORBIT , NOVAS_AIRBORNE_OBSERVER ,
  NOVAS_SOLAR_SYSTEM_OBSERVER
} enum novas_origin { NOVAS_BARYCENTER = 0 , NOVAS_HELIOCENTER } enum novas_planet {
  NOVAS_SSB = 0 , NOVAS_MERCURY , NOVAS_VENUS , NOVAS_EARTH ,
  NOVAS_MARS , NOVAS_JUPITER , NOVAS_SATURN , NOVAS_URANUS ,
  NOVAS_NEPTUNE , NOVAS_PLUTO , NOVAS_SUN , NOVAS_MOON ,
  NOVAS_EMB , NOVAS_PLUTO_BARYCENTER
} enum novas_pole_offset_type { POLE_OFFSETS_DPSI_DEPS = 1 , POLE_OFFSETS_X_Y } enum novas_reference_plane { NOVAS_ECLIPTIC_PLANE = 0 , NOVAS_EQUATORIAL_PLANE } enum novas_reference_system {
  NOVAS_GCRS = 0 , NOVAS_TOD , NOVAS_CIRS , NOVAS_ICRS ,
  NOVAS_J2000 , NOVAS_MOD , NOVAS_TIRS , NOVAS_ITRS
} enum novas_refraction_model {
  NOVAS_NO_ATMOSPHERE = 0 , NOVAS_STANDARD_ATMOSPHERE , NOVAS_WEATHER_AT_LOCATION , NOVAS_RADIO_REFRACTION ,
  NOVAS_WAVE_REFRACTION
} enum novas_refraction_type { NOVAS_REFRACT_OBSERVED = -1 , NOVAS_REFRACT_ASTROMETRIC } enum novas_separator_type { NOVAS_SEP_COLONS = 0 , NOVAS_SEP_SPACES , NOVAS_SEP_UNITS , NOVAS_SEP_UNITS_AND_SPACES } enum novas_timescale {
  NOVAS_TCB = 0 , NOVAS_TDB , NOVAS_TCG , NOVAS_TT ,
  NOVAS_TAI , NOVAS_GPS , NOVAS_UTC , NOVAS_UT1
} enum novas_transform_type {
  PROPER_MOTION = 1 , PRECESSION , CHANGE_EPOCH , CHANGE_J2000_TO_ICRS ,
  CHANGE_ICRS_TO_J2000
} enum novas_wobble_direction { WOBBLE_ITRS_TO_TIRS = 0 , WOBBLE_TIRS_TO_ITRS , WOBBLE_ITRS_TO_PEF , WOBBLE_PEF_TO_ITRS } int aberration (const double *pos, const double *vobs, double lighttime, double *out) double accum_prec (double t) short app_planet (double jd_tt, const object *restrict ss_body, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis) short app_star (double jd_tt, const cat_entry *restrict star, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec) double app_to_cirs_ra (double jd_tt, enum novas_accuracy accuracy, double ra) short astro_planet (double jd_tt, const object *restrict ss_body, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis) short astro_star (double jd_tt, const cat_entry *restrict star, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec) int bary2obs (const double *pos, const double *pos_obs, double *out, double *restrict lighttime) int cal_date (double tjd, short *restrict year, short *restrict month, short *restrict day, double *restrict hour) short cel2ter (double jd_ut1_high, double jd_ut1_low, double ut1_to_tt, enum novas_earth_rotation_measure erot, enum novas_accuracy accuracy, enum novas_equatorial_class coordType, double xp, double yp, const double *in, double *out) short cel_pole (double jd_tt, enum novas_pole_offset_type type, double dpole1, double dpole2) short cio_array (double jd_tdb, long n_pts, ra_of_cio *restrict cio) short cio_basis (double jd_tdb, double ra_cio, enum novas_cio_location_type loc_type, enum novas_accuracy accuracy, double *restrict x, double *restrict y, double *restrict z) short cio_location (double jd_tdb, enum novas_accuracy accuracy, double *restrict ra_cio, short *restrict loc_type) short cio_ra (double jd_tt, enum novas_accuracy accuracy, double *restrict ra_cio) double cirs_to_app_ra (double jd_tt, enum novas_accuracy accuracy, double ra) int cirs_to_gcrs (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) int cirs_to_itrs (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) int cirs_to_tod (double jd_tt, enum novas_accuracy accuracy, const double *in, double *out) double d_light (const double *pos_src, const double *pos_body) int e_tilt (double jd_tdb, enum novas_accuracy accuracy, double *restrict mobl, double *restrict tobl, double *restrict ee, double *restrict dpsi, double *restrict deps) int ecl2equ (double jd_tt, enum novas_equator_type coord_sys, enum novas_accuracy accuracy, double elon, double elat, double *restrict ra, double *restrict dec) short ecl2equ_vec (double jd_tt, enum novas_equator_type coord_sys, enum novas_accuracy accuracy, const double *in, double *out) double ee_ct (double jd_tt_high, double jd_tt_low, enum novas_accuracy accuracy) short ephemeris (const double *restrict jd_tdb, const object *restrict body, enum novas_origin origin, enum novas_accuracy accuracy, double *restrict pos, double *restrict vel) short equ2ecl (double jd_tt, enum novas_equator_type coord_sys, enum novas_accuracy accuracy, double ra, double dec, double *restrict elon, double *restrict elat) short equ2ecl_vec (double jd_tt, enum novas_equator_type coord_sys, enum novas_accuracy accuracy, const double *in, double *out) int equ2gal (double ra, double dec, double *restrict glon, double *restrict glat) int equ2hor (double jd_ut1, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const on_surface *restrict location, double ra, double dec, enum novas_refraction_model ref_option, double *restrict zd, double *restrict az, double *restrict rar, double *restrict decr) double era (double jd_ut1_high, double jd_ut1_low) int frame_tie (const double *in, enum novas_frametie_direction direction, double *out) int fund_args (double t, novas_delaunay_args *restrict a) int gal2equ (double glon, double glat, double *restrict ra, double *restrict dec) short gcrs2equ (double jd_tt, enum novas_dynamical_type sys, enum novas_accuracy accuracy, double rag, double decg, double *restrict ra, double *restrict dec) int gcrs_to_cirs (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) int gcrs_to_j2000 (const double *in, double *out) int gcrs_to_mod (double jd_tdb, const double *in, double *out) int gcrs_to_tod (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) short geo_posvel (double jd_tt, double ut1_to_tt, enum novas_accuracy accuracy, const observer *restrict obs, double *restrict pos, double *restrict vel) novas_nutation_provider get_nutation_lp_provider () double get_ut1_to_tt (int leap_seconds, double dut1) double get_utc_to_tt (int leap_seconds) short grav_def (double jd_tdb, enum novas_observer_place unused, enum novas_accuracy accuracy, const double *pos_src, const double *pos_obs, double *out) int grav_planets (const double *pos_src, const double *pos_obs, const novas_planet_bundle *restrict planets, double *out) double grav_redshift (double M_kg, double r_m) int grav_undef (double jd_tdb, enum novas_accuracy accuracy, const double *pos_app, const double *pos_obs, double *out) int grav_undo_planets (const double *pos_app, const double *pos_obs, const novas_planet_bundle *restrict planets, double *out) int grav_vec (const double *pos_src, const double *pos_obs, const double *pos_body, double rmass, double *out) int hor_to_itrs (const on_surface *restrict location, double az, double za, double *restrict itrs) double ira_equinox (double jd_tdb, enum novas_equinox_type equinox, enum novas_accuracy accuracy) int itrs_to_cirs (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) int itrs_to_hor (const on_surface *restrict location, const double *restrict itrs, double *restrict az, double *restrict za) int itrs_to_tod (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) int j2000_to_gcrs (const double *in, double *out) int j2000_to_tod (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) double julian_date (short year, short month, short day, double hour) short light_time (double jd_tdb, const object *restrict body, const double *pos_obs, double tlight0, enum novas_accuracy accuracy, double *pos_src_obs, double *restrict tlight) int light_time2 (double jd_tdb, const object *restrict body, const double *restrict pos_obs, double tlight0, enum novas_accuracy accuracy, double *p_src_obs, double *restrict v_ssb, double *restrict tlight) int limb_angle (const double *pos_src, const double *pos_obs, double *restrict limb_ang, double *restrict nadir_ang) short local_planet (double jd_tt, const object *restrict ss_body, double ut1_to_tt, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis) short local_star (double jd_tt, double ut1_to_tt, const cat_entry *restrict star, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec) int make_airborne_observer (const on_surface *location, const double *vel, observer *obs) short make_cat_entry (const char *restrict star_name, const char *restrict catalog, long cat_num, double ra, double dec, double pm_ra, double pm_dec, double parallax, double rad_vel, cat_entry *star) int make_cat_object (const cat_entry *star, object *source) int make_cat_object_sys (const cat_entry *star, const char *restrict system, object *source) int make_ephem_object (const char *name, long num, object *body) int make_in_space (const double *sc_pos, const double *sc_vel, in_space *loc) short make_object (enum novas_object_type, long number, const char *name, const cat_entry *star, object *source) short make_observer (enum novas_observer_place, const on_surface *loc_surface, const in_space *loc_space, observer *obs) int make_observer_at_geocenter (observer *restrict obs) int make_observer_in_space (const double *sc_pos, const double *sc_vel, observer *obs) int make_observer_on_surface (double latitude, double longitude, double height, double temperature, double pressure, observer *restrict obs) int make_on_surface (double latitude, double longitude, double height, double temperature, double pressure, on_surface *restrict loc) int make_planet (enum novas_planet num, object *restrict planet) int make_redshifted_cat_entry (const char *name, double ra, double dec, double z, cat_entry *source) int make_redshifted_object (const char *name, double ra, double dec, double z, object *source) int make_redshifted_object_sys (const char *name, double ra, double dec, const char *restrict system, double z, object *source) int make_solar_system_observer (const double *sc_pos, const double *sc_vel, observer *obs) double mean_obliq (double jd_tdb) short mean_star (double jd_tt, double tra, double tdec, enum novas_accuracy accuracy, double *restrict ira, double *restrict idec) int mod_to_gcrs (double jd_tdb, const double *in, double *out) int novas_app_to_geom (const novas_frame *restrict frame, enum novas_reference_system sys, double ra, double dec, double dist, double *restrict geom_icrs) int novas_app_to_hor (const novas_frame *restrict frame, enum novas_reference_system sys, double ra, double dec, RefractionModel ref_model, double *restrict az, double *restrict el) void novas_case_sensitive (int value) int novas_change_observer (const novas_frame *orig, const observer *obs, novas_frame *out) double novas_date (const char *restrict date) double novas_date_scale (const char *restrict date, enum novas_timescale *restrict scale) int novas_day_of_week (double tjd) int novas_day_of_year (double tjd, enum novas_calendar_type calendar, int *restrict year) void novas_debug (enum novas_debug_mode mode) ==========================================================================
double novas_diff_tcb (const novas_timespec *t1, const novas_timespec *t2) double novas_diff_tcg (const novas_timespec *t1, const novas_timespec *t2) double novas_diff_time (const novas_timespec *t1, const novas_timespec *t2) double novas_dms_degrees (const char *restrict dms) int novas_e2h_offset (double dra, double ddec, double pa, double *restrict daz, double *restrict del) double novas_epa (double ha, double dec, double lat) double novas_epoch (const char *restrict system) double novas_equ_sep (double ra1, double dec1, double ra2, double dec2) int novas_equ_track (const object *restrict source, const novas_frame *restrict frame, double dt, novas_track *restrict track) double novas_frame_lst (const novas_frame *restrict frame) int novas_geom_posvel (const object *restrict source, const novas_frame *restrict frame, enum novas_reference_system sys, double *restrict pos, double *restrict vel) int novas_geom_to_app (const novas_frame *restrict frame, const double *restrict pos, enum novas_reference_system sys, sky_pos *restrict out) enum novas_debug_mode novas_get_debug_mode () double novas_get_split_time (const novas_timespec *restrict time, enum novas_timescale timescale, long *restrict ijd) double novas_get_time (const novas_timespec *restrict time, enum novas_timescale timescale) time_t novas_get_unix_time (const novas_timespec *restrict time, long *restrict nanos) int novas_h2e_offset (double daz, double del, double pa, double *restrict dra, double *restrict ddec) double novas_hms_hours (const char *restrict hms) int novas_hor_to_app (const novas_frame *restrict frame, double az, double el, RefractionModel ref_model, enum novas_reference_system sys, double *restrict ra, double *restrict dec) int novas_hor_track (const object *restrict source, const novas_frame *restrict frame, RefractionModel ref_model, novas_track *restrict track) double novas_hpa (double az, double el, double lat) double novas_inv_refract (RefractionModel model, double jd_tt, const on_surface *restrict loc, enum novas_refraction_type type, double el0) int novas_invert_transform (const novas_transform *transform, novas_transform *inverse) int novas_iso_timestamp (const novas_timespec *restrict time, char *restrict dst, int maxlen) double novas_jd_from_date (enum novas_calendar_type calendar, int year, int month, int day, double hour) int novas_jd_to_date (double tjd, enum novas_calendar_type calendar, int *restrict year, int *restrict month, int *restrict day, double *restrict hour) int novas_los_to_xyz (const double *los, double lon, double lat, double *xyz) double novas_lsr_to_ssb_vel (double epoch, double ra, double dec, double vLSR) int novas_make_frame (enum novas_accuracy accuracy, const observer *obs, const novas_timespec *time, double dx, double dy, novas_frame *frame) int novas_make_transform (const novas_frame *frame, enum novas_reference_system from_system, enum novas_reference_system to_system, novas_transform *transform) double novas_norm_ang (double angle) double novas_object_sep (const object *source1, const object *source2, const novas_frame *restrict frame) int novas_offset_time (const novas_timespec *time, double seconds, novas_timespec *out) double novas_optical_refraction (double jd_tt, const on_surface *loc, enum novas_refraction_type type, double el) double novas_parse_date (const char *restrict date, char **restrict tail) double novas_parse_date_format (enum novas_calendar_type calendar, enum novas_date_format format, const char *restrict date, char **restrict tail) double novas_parse_degrees (const char *restrict str, char **restrict tail) double novas_parse_dms (const char *restrict str, char **restrict tail) double novas_parse_hms (const char *restrict str, char **restrict tail) double novas_parse_hours (const char *restrict str, char **restrict tail) double novas_parse_iso_date (const char *restrict date, char **restrict tail) enum novas_timescale novas_parse_timescale (const char *restrict str, char **restrict tail) int novas_print_dms (double degrees, enum novas_separator_type sep, int decimals, char *restrict buf, int len) int novas_print_hms (double hours, enum novas_separator_type sep, int decimals, char *restrict buf, int len) int novas_print_timescale (enum novas_timescale scale, char *restrict buf) double novas_radio_refraction (double jd_tt, const on_surface *loc, enum novas_refraction_type type, double el) int novas_refract_wavelength (double microns) double novas_rises_above (double el, const object *restrict source, const novas_frame *restrict frame, RefractionModel ref_model) double novas_sep (double lon1, double lat1, double lon2, double lat2) int novas_set_split_time (enum novas_timescale timescale, long ijd, double fjd, int leap, double dut1, novas_timespec *restrict time) int novas_set_time (enum novas_timescale timescale, double jd, int leap, double dut1, novas_timespec *restrict time) int novas_set_unix_time (time_t unix_time, long nanos, int leap, double dut1, novas_timespec *restrict time) double novas_sets_below (double el, const object *restrict source, const novas_frame *restrict frame, RefractionModel ref_model) int novas_sky_pos (const object *restrict object, const novas_frame *restrict frame, enum novas_reference_system sys, sky_pos *restrict out) double novas_ssb_to_lsr_vel (double epoch, double ra, double dec, double vLSR) double novas_standard_refraction (double jd_tt, const on_surface *loc, enum novas_refraction_type type, double el) double novas_str_degrees (const char *restrict dms) double novas_str_hours (const char *restrict hms) double novas_time_gst (const novas_timespec *restrict time, enum novas_accuracy accuracy) double novas_time_lst (const novas_timespec *restrict time, double lon, enum novas_accuracy accuracy) enum novas_timescale novas_timescale_for_string (const char *restrict str) int novas_timestamp (const novas_timespec *restrict time, enum novas_timescale scale, char *restrict dst, int maxlen) int novas_track_pos (const novas_track *track, const novas_timespec *time, double *restrict lon, double *restrict lat, double *restrict dist, double *restrict z) int novas_transform_sky_pos (const sky_pos *in, const novas_transform *restrict transform, sky_pos *out) int novas_transform_vector (const double *in, const novas_transform *restrict transform, double *out) double novas_transit_time (const object *restrict source, const novas_frame *restrict frame) int novas_uvw_to_xyz (const double *uvw, double ha, double dec, double *xyz) double novas_v2z (double vel) double novas_wave_refraction (double jd_tt, const on_surface *loc, enum novas_refraction_type type, double el) int novas_xyz_to_los (const double *xyz, double lon, double lat, double *los) int novas_xyz_to_uvw (const double *xyz, double ha, double dec, double *uvw) double novas_z2v (double z) ==========================================================================
double novas_z_add (double z1, double z2) double novas_z_inv (double z) int nutation (double jd_tdb, enum novas_nutation_direction direction, enum novas_accuracy accuracy, const double *in, double *out) int nutation_angles (double t, enum novas_accuracy accuracy, double *restrict dpsi, double *restrict deps) int obs_planets (double jd_tdb, enum novas_accuracy accuracy, const double *restrict pos_obs, int pl_mask, novas_planet_bundle *restrict planets) int obs_posvel (double jd_tdb, double ut1_to_tt, enum novas_accuracy accuracy, const observer *restrict obs, const double *restrict geo_pos, const double *restrict geo_vel, double *restrict pos, double *restrict vel) short place (double jd_tt, const object *restrict source, const observer *restrict location, double ut1_to_tt, enum novas_reference_system coord_sys, enum novas_accuracy accuracy, sky_pos *restrict output) int place_cirs (double jd_tt, const object *restrict source, enum novas_accuracy accuracy, sky_pos *restrict pos) int place_gcrs (double jd_tt, const object *restrict source, enum novas_accuracy accuracy, sky_pos *restrict pos) int place_icrs (double jd_tt, const object *restrict source, enum novas_accuracy accuracy, sky_pos *restrict pos) int place_j2000 (double jd_tt, const object *restrict source, enum novas_accuracy accuracy, sky_pos *restrict pos) int place_mod (double jd_tt, const object *restrict source, enum novas_accuracy accuracy, sky_pos *restrict pos) int place_star (double jd_tt, const cat_entry *restrict star, const observer *restrict obs, double ut1_to_tt, enum novas_reference_system system, enum novas_accuracy accuracy, sky_pos *restrict pos) int place_tod (double jd_tt, const object *restrict source, enum novas_accuracy accuracy, sky_pos *restrict pos) double planet_lon (double t, enum novas_planet planet) short precession (double jd_tdb_in, const double *in, double jd_tdb_out, double *out) int proper_motion (double jd_tdb_in, const double *pos, const double *restrict vel, double jd_tdb_out, double *out) int rad_vel (const object *restrict source, const double *restrict pos_src, const double *vel_src, const double *vel_obs, double d_obs_geo, double d_obs_sun, double d_src_sun, double *restrict rv) double rad_vel2 (const object *restrict source, const double *pos_emit, const double *vel_src, const double *pos_det, const double *vel_obs, double d_obs_geo, double d_obs_sun, double d_src_sun) int radec2vector (double ra, double dec, double dist, double *restrict pos) int radec_planet (double jd_tt, const object *restrict ss_body, const observer *restrict obs, double ut1_to_tt, enum novas_reference_system sys, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis, double *restrict rv) int radec_star (double jd_tt, const cat_entry *restrict star, const observer *restrict obs, double ut1_to_tt, enum novas_reference_system sys, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict rv) double redshift_vrad (double vrad, double z) double refract (const on_surface *restrict location, enum novas_refraction_model model, double zd_obs) double refract_astro (const on_surface *restrict location, enum novas_refraction_model model, double zd_astro) int set_cio_locator_file (const char *restrict filename) int set_nutation_lp_provider (novas_nutation_provider func) short sidereal_time (double jd_ut1_high, double jd_ut1_low, double ut1_to_tt, enum novas_equinox_type gst_type, enum novas_earth_rotation_measure erot, enum novas_accuracy accuracy, double *restrict gst) int spin (double angle, const double *in, double *out) int starvectors (const cat_entry *restrict star, double *restrict pos, double *restrict motion) int tdb2tt (double jd_tdb, double *restrict jd_tt, double *restrict secdiff) short ter2cel (double jd_ut1_high, double jd_ut1_low, double ut1_to_tt, enum novas_earth_rotation_measure erot, enum novas_accuracy accuracy, enum novas_equatorial_class coordType, double xp, double yp, const double *in, double *out) int terra (const on_surface *restrict location, double lst, double *restrict pos, double *restrict vel) int tod_to_cirs (double jd_tt, enum novas_accuracy accuracy, const double *in, double *out) int tod_to_gcrs (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) int tod_to_itrs (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) int tod_to_j2000 (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) short topo_planet (double jd_tt, const object *restrict ss_body, double ut1_to_tt, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis) short topo_star (double jd_tt, double ut1_to_tt, const cat_entry *restrict star, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec) short transform_cat (enum novas_transform_type, double jd_tt_in, const cat_entry *in, double jd_tt_out, const char *out_id, cat_entry *out) int transform_hip (const cat_entry *hipparcos, cat_entry *hip_2000) double tt2tdb (double jd_tt) double tt2tdb_fp (double jd_tt, double limit) double tt2tdb_hp (double jd_tt) double unredshift_vrad (double vrad, double z) short vector2radec (const double *restrict pos, double *restrict ra, double *restrict dec) short virtual_planet (double jd_tt, const object *restrict ss_body, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis) short virtual_star (double jd_tt, const cat_entry *restrict star, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec) int wobble (double jd_tt, enum novas_wobble_direction direction, double xp, double yp, const double *in, double *out)

Version: 1.3.0

SuperNOVAS astrometry software based on the Naval Observatory Vector Astrometry Software (NOVAS). It has been modified to fix outstanding issues and to make it easier to use.

Based on the NOVAS C Edition, Version 3.1:

U. S. Naval Observatory
Astronomical Applications Dept.
Washington, DC
http://www.usno.navy.mil/USNO/astronomical-applications

◆ BARYC

Deprecated:: Old definition of the Barycenter origin. NOVAS_BARYCENTER is preferred.

◆ CAT_ENTRY_INIT #define CAT_ENTRY_INIT { {'\0'}, {'\0'}, 0L, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }

Initializer for a NOVAS cat_entry structure.

See also: cat_entry

Author: Attila Kovacs

Since: 1.1.1

◆ DE405_AU #define DE405_AU 1.4959787069098932e+11

[m] Astronomical unit (AU). based on DE-405. (old definition)

See also: NOVAS_AU

◆ DEFAULT_CIO_LOCATOR_FILE #define DEFAULT_CIO_LOCATOR_FILE "/usr/share/novas/cio_ra.bin"

Path / name of file to use for interpolating the CIO location relative to GCRS This file can be generated with the cio_file.c tool using the CIO_RA.TXT data (both are included in the distribution)

◆ DEFAULT_GRAV_BODIES_FULL_ACCURACY

Default set of gravitating bodies to use for deflection calculations in full accuracy mode.

See also: grav_bodies_full_accuracy

Since: 1.1

Author: Attila Kovacs

◆ DEFAULT_GRAV_BODIES_REDUCED_ACCURACY #define DEFAULT_GRAV_BODIES_REDUCED_ACCURACY ( (1 << NOVAS_SUN) )

Default set of gravitating bodies to use for deflection calculations in reduced accuracy mode. (only apply gravitational deflection for the Sun.)

See also: grav_bodies_reduced_accuracy

Since: 1.1

Author: Attila Kovacs

◆ HELIOC

Deprecated:: Old definition of the Center of Sun as the origin. NOVAS_HELIOCENTER is preferred.

◆ IN_SPACE_INIT #define IN_SPACE_INIT {{0.0}, {0.0}}

Initializer for a NOVAS in_space structure.

See also: in_space

Since: 1.1.1

Author: Attila Kovacs

◆ NOVAS_ARCMIN

[rad] An arc minute expressed in radians.

Since: 1.2

◆ NOVAS_ARCSEC

[rad] An arc second expressed in radians.

Since: 1.2

◆ NOVAS_AU #define NOVAS_AU 1.495978707e+11 ◆ NOVAS_DAY #define NOVAS_DAY 86400.0

[s] The length of a synodic day, that is 24 hours exactly.

Since: 1.2

◆ NOVAS_DEFAULT_WAVELENGTH #define NOVAS_DEFAULT_WAVELENGTH 0.55

[μm] Default wavelength, e.g. for wavelength-dependent refraction models. It is set to the median wavelength of visible light.

Since: 1.4

◆ NOVAS_DEGREE #define NOVAS_DEGREE (M_PI / 180.0)

[rad] A degree expressed in radians.

Since: 1.2

◆ NOVAS_DELAUNAY_ARGS_INIT #define NOVAS_DELAUNAY_ARGS_INIT { 0.0, 0.0, 0.0, 0.0, 0.0 } ◆ NOVAS_EARTH_INIT

object initializer for the planet Earth

Since: 1.2

See also: object

◆ NOVAS_EMB_INIT

object initializer for the the Earth-Moon Barycenter (EMB)

Since: 1.2

See also: object

◆ NOVAS_EQUATOR_TYPES

The number of equator types defined in enum novas_equator_type.

See also: enum novas_equator_type

Since: 1.2

◆ NOVAS_FRAME_INIT Value:

{ 0,

NOVAS_FULL_ACCURACY

NOVAS_TIMESPEC_INIT

OBSERVER_INIT

, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, \

0.0, 0.0, {0.0}, {0.0}, 0.0, 0.0, 0.0, {0.0}, {0.0}, {0.0}, {0.0},

NOVAS_MATRIX_INIT

, \

@ NOVAS_FULL_ACCURACY

Definition novas.h:524

#define NOVAS_PLANET_BUNDLE_INIT

Definition novas.h:1304

#define OBSERVER_INIT

Definition novas.h:1164

#define NOVAS_MATRIX_INIT

Definition novas.h:1273

#define NOVAS_TIMESPEC_INIT

Definition novas.h:1253

Empty initializer for novas_frame

Since: 1.3

See also: novas_frame

◆ NOVAS_HOURANGLE #define NOVAS_HOURANGLE (M_PI / 12.0)

[rad] An hour of angle expressed in radians.

Since: 1.2

◆ NOVAS_JD_START_GREGORIAN #define NOVAS_JD_START_GREGORIAN 2299160.5

[day] The Julian day the Gregorian calendar was introduced in 15 October 1582. The day prior to that was 4 October 1582 in the Julian Calendar.

◆ NOVAS_JUPITER_INIT

object initializer for the planet Jupiter

Since: 1.2

See also: object

◆ NOVAS_KM

[m] A kilometer (km) in meters.

Since: 1.2

◆ NOVAS_KMS

[m] One km/s in m/s.

Since: 1.3

◆ NOVAS_MARS_INIT

object initializer for the planet Mars

Since: 1.2

See also: object

◆ NOVAS_MATRIX_IDENTITY #define NOVAS_MATRIX_IDENTITY {{{1.0, 0.0, 0.0}, {0.0, 1.0, 0.0}, {0.0, 0.0, 1.0}}} ◆ NOVAS_MATRIX_INIT #define NOVAS_MATRIX_INIT {{{0.0}}} ◆ NOVAS_MERCURY_INIT

object initializer for the planet Venus

Since: 1.2

See also: object

◆ NOVAS_MOON_INIT

object initializer for the Moon

Since: 1.2

See also: object

◆ NOVAS_NEPTUNE_INIT

object initializer for the planet Neptune

Since: 1.2

See also: object

◆ NOVAS_OBJECT_INIT

Empty object initializer.

Since: 1.3

Author: Attila Kovacs

See also: object

◆ NOVAS_OBJECT_TYPES ◆ NOVAS_OBSERVABLE_INIT #define NOVAS_OBSERVABLE_INIT { 0.0, 0.0, 0.0, 0.0 } ◆ NOVAS_OBSERVER_PLACES ◆ NOVAS_ORBIT_INIT #define NOVAS_ORBIT_INIT { NOVAS_ORBITAL_SYSTEM_INIT, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }

Initializer for novas_orbital for heliocentric orbits using GCRS ecliptic pqrametrization.

See also: novas_orbital

Author: Attila Kovacs

Since: 1.2

◆ NOVAS_ORBITAL_SYSTEM_INIT

Default orbital system initializer for heliocentric GCRS ecliptic orbits.

See also: novas_orbital_system

Author: Attila Kovacs

Since: 1.2

◆ NOVAS_ORIGIN_TYPES

The number of different ICSR origins available in NOVAS.

See also: enum novas_origin

◆ NOVAS_PLANET_BUNDLE_INIT #define NOVAS_PLANET_BUNDLE_INIT { 0, {{0.0}}, {{0.0}} } ◆ NOVAS_PLANET_GRAV_Z_INIT #define NOVAS_PLANET_GRAV_Z_INIT Value:

{ \

0.0, 1.0047e-10, 5.9724e-10, 7.3050e-10, 1.4058e-10, 2.0166e-8, 7.2491e-9, 2.5420e-9, \

3.0893e-9, 9.1338e-12, 2.120483e-6, 3.1397e-11, 0.0, 0.0 }

Gravitational redshifts for major planets (and Moon and Sun) for light emitted at surface and detected at a large distance away. Barycenters are not considered, and for Pluto the redshift for the Pluto system is assumed for distant observers.

See also: enum novas_planet; NOVAS_PLANETS

Since: 1.1.1

Author: Attila Kovacs

◆ NOVAS_PLANET_INIT

object initializer macro for major planets, the Sun, Moon, and barycenters.

Parameters: num An enum novas_planet number name The designated planet name

Since: 1.2

◆ NOVAS_PLANET_NAMES_INIT #define NOVAS_PLANET_NAMES_INIT Value:

{ \

"SSB", "Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune", "Pluto", \

"Sun", "Moon", "EMB", "Pluto-Barycenter" }

String array initializer for Major planet names, matching the enum novas_planet. E.g.

#define NOVAS_PLANET_NAMES_INIT

Definition novas.h:346

See also: novas_majot_planet

Since: 1.2

Author: Attila Kovacs

◆ NOVAS_PLANETS

The number of major planets defined in NOVAS.

See also: enum novas_planet

◆ NOVAS_PLUTO_BARYCENTER_INIT

object initializer for the Pluto system barycenter

Since: 1.2

See also: object

◆ NOVAS_PLUTO_INIT

object initializer for the minor planet Pluto

Since: 1.2

See also: object

◆ NOVAS_REFERENCE_SYSTEMS ◆ NOVAS_REFRACTION_MODELS ◆ NOVAS_RMASS_INIT Value:

{ \

328900.559708565, 6023657.9450387, 408523.718656268, 332946.048773067, 3098703.54671961, \

1047.348631244, 3497.9018007932, 22902.9507834766, 19412.2597758766, 136045556.16738, \

1.0, 27068702.9548773, 0.0, 0.0 }

Reciprocal masses of solar system bodies, from DE-405 (Sun mass / body mass). [0]: Earth/Moon barycenter (legacy from NOVAS C), MASS[1] = Mercury, ...,

Barycentric reciprocal masses (index 12, 13) are not set.

NOTES:

The values have been updated to used DE440 data (Park et al. 2021) in 1.4.

REFERENCES:

Ryan S. Park et al 2021 AJ 161 105, DOI 10.3847/1538-3881/abd414

See also: enum novas_planet; NOVAS_PLANETS

Since: 1.2

Author: Attila Kovacs

◆ NOVAS_SATURN_INIT

object initializer for the planet Saturn

Since: 1.2

See also: object

◆ NOVAS_SOLAR_CONSTANT #define NOVAS_SOLAR_CONSTANT 1367.0

[W/m²] The Solar Constant i.e., typical incident Solar power on Earth. The value of 1367 Wm⁻² was adopted by the World Radiation Center (Gueymard, 2004).

Since: 1.3

◆ NOVAS_SOLAR_RADIUS #define NOVAS_SOLAR_RADIUS 696340000.0

[m] Solar radius (photosphere)

Since: 1.1

◆ NOVAS_SSB_INIT

object initializer for the Solar System Barycenter (SSB)

Since: 1.2

See also: object

◆ NOVAS_SUN_INIT

object initializer for the Sun

Since: 1.2

See also: object

◆ NOVAS_SYSTEM_B1950 #define NOVAS_SYSTEM_B1950 "B1950"

The B1950 coordiante system as a string

Since: 1.3

◆ NOVAS_SYSTEM_FK4 #define NOVAS_SYSTEM_FK4 "FK4"

The 4th catalog (FK4) coordinate system as a string

Since: 1.3

◆ NOVAS_SYSTEM_FK5 #define NOVAS_SYSTEM_FK5 "FK5"

The 5th catalog (FK5) coordinate system as a string

Since: 1.3

◆ NOVAS_SYSTEM_HIP #define NOVAS_SYSTEM_HIP "HIP"

The Hipparcos dataset coordinate system as a string

Since: 1.3

◆ NOVAS_SYSTEM_ICRS #define NOVAS_SYSTEM_ICRS "ICRS"

The ICRS system as a string

Since: 1.3

◆ NOVAS_SYSTEM_J2000 #define NOVAS_SYSTEM_J2000 "J2000"

The J2000 coordinate syste, as a string

Since: 1.3

◆ NOVAS_TIMESCALES

The number of asronomical time scales supported.

See also: novas_timescale

Since: 1.1

◆ NOVAS_TIMESPEC_INIT #define NOVAS_TIMESPEC_INIT { 0, 0.0, 0.0, 0.0, 0.0 } ◆ NOVAS_TRACK_INIT ◆ NOVAS_TRANSFORM_INIT ◆ NOVAS_TRANSFORM_TYPES ◆ NOVAS_URANUS_INIT

object initializer for the planet Uranus

Since: 1.2

See also: object

◆ NOVAS_VENUS_INIT

object initializer for the planet Mercury

Since: 1.2

See also: object

◆ NOVAS_WOBBLE_DIRECTIONS ◆ OBSERVER_INIT

Empty initializer for observer

Since: 1.3

Author: Attila Kovacs

See also: observer

◆ ON_SURFACE_INIT #define ON_SURFACE_INIT { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 } ◆ ON_SURFACE_LOC #define ON_SURFACE_LOC ( lon, lat, alt ) { lon, lat, alt, 0.0, 0.0, 0.0 }

Initializer for a NOVAS on_surface data structure at a specified geodetic location

Parameters: lon [deg] Geodetic longitude of observer (East is positive) lat [deg] Geodetic latitude of observer (North is positive) alt [m] Observer altitude above sea level.

See also: on_surface; ON_SURFACE_INIT

Since: 1.2

Author: Attila Kovacs

◆ SKY_POS_INIT #define SKY_POS_INIT { {0.0}, 0.0, 0.0, 0.0, 0.0 }

Initializer for a NOVAS sky_pos structure.

See also: sky_pos

Since: 1.1.1

Author: Attila Kovacs

◆ SUPERNOVAS_VERSION_STRING #define SUPERNOVAS_VERSION_STRING

The version string for this library

◆ RefractionModel

A function that returns a refraction correction for a given date/time of observation at the given site on earth, and for a given astrometric source elevation

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian data of observation loc Pointer to structure defining the observer's location on earth, and local weather type Whether the input elevation is observed or astrometric: REFRACT_OBSERVED (-1) or REFRACT_ASTROMETRIC (0). el [deg] Astrometric (unrefracted) source elevation

Returns: [arcsec] Estimated refraction, or NAN if there was an error (it should also set errno to indicate the type of error).

Since: 1.1

◆ novas_accuracy

Constants to control the precision of NOVAS nutation calculations.

Enumerator NOVAS_FULL_ACCURACY

Use full precision calculations to micro-arcsecond accuracy. It can be computationally intensive when using the dynamical equator.

NOVAS_REDUCED_ACCURACY

Calculate with truncated terms. It can be significantly faster if a few milliarcsecond accuracy is sufficient.

◆ novas_calendar_type

Constants to disambiguate which type of calendar yo use for interpreting calendar dates. Roman/Julian or Gregorian/

Since: 1.3

Author: Attila Kovacs

See also: novas_jd_from_date(); novas_jd_to_date()

Enumerator NOVAS_ROMAN_CALENDAR

The Roman (a.k.a. Julian) calendar by Julius Caesar, introduced in -45 B.C.

NOVAS_ASTRONOMICAL_CALENDAR

Roman (a.k.a. Julian) calendar until the Gregorian calendar reform of 1582, after which it is the Gregorian calendar

NOVAS_GREGORIAN_CALENDAR

The Gregorian calendar introduced on 15 October 1582, the day after 4 October 1582 in the Roman (a.k.a. Julian) calendar.

◆ novas_cio_location_type

System in which CIO location is calculated.

Enumerator CIO_VS_GCRS

The location of the CIO relative to the GCRS frame.

CIO_VS_EQUINOX

The location of the CIO relative to the true equinox in the dynamical frame.

◆ novas_date_format

The general order of date components for parsing.

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_date_format()

Enumerator NOVAS_YMD

year, then month, then day.

NOVAS_DMY

day, then month, then year

NOVAS_MDY

month, then day, then year

◆ novas_debug_mode

Settings for 'novas_debug()'

See also: novas_debug

Enumerator NOVAS_DEBUG_OFF

Do not print errors and traces to the standard error (default).

NOVAS_DEBUG_ON

Print errors and traces to the standard error.

NOVAS_DEBUG_EXTRA

Print all errors and traces to the standard error, even if they may be acceptable behavior.

◆ novas_dynamical_type

Constants that determine the type of dynamical system. I.e., the 'current' equatorial coordinate system used for a given epoch of observation.

Enumerator NOVAS_DYNAMICAL_MOD

Mean equinox Of Date (TOD): dynamical system not including nutation (pre IAU 2006 system).

NOVAS_DYNAMICAL_TOD

True equinox Of Date (TOD): dynamical system of the 'true' equator, with its origin at the true equinox (pre IAU 2006 system; Lieske et. al. 1977).

NOVAS_DYNAMICAL_CIRS

Celestial Intermediate Reference System (CIRS): dynamical system of the true equator, with its origin at the CIO (preferred since IAU 2006)

◆ novas_earth_rotation_measure

Constants that determine the type of rotation measure to use.

Enumerator EROT_ERA

Use Earth Rotation Angle (ERA) as the rotation measure, relative to the CIO (new IAU 2006 standard)

EROT_GST

Use GST as the rotation measure, relative to the true equinox (pre IAU 20006 standard)

◆ novas_equator_type

Constants that determine the type of equator to be used for the coordinate system.

See also: NOVAS_EQUATOR_TYPES

Enumerator NOVAS_MEAN_EQUATOR

Mean celestial equator of date without nutation (pre IAU 2006 system).

NOVAS_TRUE_EQUATOR

True celestial equator of date (pre IAU 2006 system).

NOVAS_GCRS_EQUATOR

Geocentric Celestial Reference System (GCRS) equator.

◆ novas_equatorial_class

The class of celestial coordinates used as parameters for ter2cel() and cel2ter().

Enumerator NOVAS_REFERENCE_CLASS

Celestial coordinates are in GCRS.

NOVAS_DYNAMICAL_CLASS

Celestial coordinates are apparent values (CIRS or TOD)

◆ novas_equinox_type

The type of equinox used in the pre IAU 2006 (old) methodology.

Enumerator NOVAS_TRUE_EQUINOX

Mean equinox: includes precession but not nutation.

True apparent equinox: includes both precession and nutation

◆ novas_frametie_direction

Direction constant to use for frame_tie(), to determine the direction of transformation between J2000 and ICRS coordinates.

See also: frame_tie(); J2000_TO_ICRS

Enumerator J2000_TO_ICRS

Change coordinates from ICRS to the J2000 (dynamical) frame. (You can also use any negative value for the same effect).

ICRS_TO_J2000

Change coordinates from J2000 (dynamical) frame to the ICRS. (You can use any value >=0 for the same effect).

◆ novas_nutation_direction

Direction constant for nutation(), between mean and true equatorial coordinates.

Enumerator NUTATE_TRUE_TO_MEAN

Change from true equator to mean equator (i.e. undo wobble corrections). You may use any non-zero value as well.

NUTATE_MEAN_TO_TRUE

Change from mean equator to true equator (i.e. apply wobble corrections)

◆ novas_object_type

The type of astronomical objects distinguied by the NOVAS library.

See also: NOVAS_OBJECT_TYPES

Enumerator NOVAS_PLANET

A major planet, or else the Sun, the Moon, or the Solar-System Barycenter (SSB).

See also: enum novas_planet; novas_planet_provider; novas_planet_provider_hp

NOVAS_EPHEM_OBJECT

A Solar-system body that does not fit the major planet type, and requires specific user-provided novas_ephem_provider implementation.

See also: novas_ephem_provider

NOVAS_CATALOG_OBJECT

Any non-solar system object that may be handled via 'catalog' coordinates, such as a star or a quasar.

See also: cat_entry

NOVAS_ORBITAL_OBJECT

Any Solar-system body, whose position is determined by a set of orbital elements

Since: 1.2

See also: novas_orbital

◆ novas_observer_place

Types of places on and around Earth that may serve a a reference position for the observation.

See also: NOVAS_OBSERVER_PLACES

Enumerator NOVAS_OBSERVER_AT_GEOCENTER

Calculate coordinates as if observing from the geocenter for location and Earth rotation independent coordinates.

NOVAS_OBSERVER_ON_EARTH

Stationary observer in the corotating frame of Earth.

NOVAS_OBSERVER_IN_EARTH_ORBIT

Observer is on Earth orbit, with a position and velocity vector relative to geocenter. This may also be appropriate for observatories at the L2 or other Earth-based Langrange points.

NOVAS_AIRBORNE_OBSERVER

Observer airborne, moving relative to the surface of Earth.

Since: 1.1

NOVAS_SOLAR_SYSTEM_OBSERVER

Observer is orbiting the Sun.

Since: 1.1

◆ novas_origin

The origin of the ICRS system for referencing positions and velocities for solar-system bodies.

See also: NOVAS_ORIGIN_TYPES

Enumerator NOVAS_BARYCENTER

Origin at the Solar-system baricenter (i.e. BCRS)

NOVAS_HELIOCENTER

Origin at the center of the Sun.

◆ novas_planet

Enumeration for the 'major planet' numbers in NOVAS to use as the solar-system body number whenever the object type is NOVAS_PLANET.

See also: NOVAS_PLANET; NOVAS_PLANETS; NOVAS_PLANET_NAMES_INIT

Enumerator NOVAS_SSB

Solar-system barycenter position ID.

NOVAS_MERCURY

Major planet number for Mercury in NOVAS.

NOVAS_VENUS

Major planet number for Venus in NOVAS.

NOVAS_EARTH

Major planet number for Earth in NOVAS.

NOVAS_MARS

Major planet number for Mars in NOVAS.

NOVAS_JUPITER

Major planet number for Jupiter in NOVAS.

NOVAS_SATURN

Major planet number for Saturn in NOVAS.

NOVAS_URANUS

Major planet number for Uranus in NOVAS.

NOVAS_NEPTUNE

Major planet number for Neptune in NOVAS.

NOVAS_PLUTO

Major planet number for Pluto in NOVAS.

NOVAS_SUN

Numerical ID for the Sun in NOVAS.

NOVAS_MOON

Numerical ID for the Moon in NOVAS.

NOVAS_EMB

NOVAS ID for the Earth-Moon Barycenter (EMB).

Since: 1.2

NOVAS_PLUTO_BARYCENTER

NOVAS ID for the barycenter of the Pluto System.

Since: 1.2

◆ novas_pole_offset_type

The convention in which the celestial pole offsets are defined for polar wobble.

Enumerator POLE_OFFSETS_DPSI_DEPS

Offsets are Δdψ, Δdε pairs (pre IAU 2006 precession-nutation model).

POLE_OFFSETS_X_Y

Offsets are dx, dy pairs (IAU 2006 precession-nutation model)

◆ novas_reference_plane

The plane in which values, such as orbital parameyters are referenced.

Author: Attila Kovacs

Since: 1.2

Enumerator NOVAS_ECLIPTIC_PLANE

the plane of the ecliptic

NOVAS_EQUATORIAL_PLANE

The plane of the equator.

◆ novas_reference_system

The basic types of positional coordinate reference systems supported by NOVAS. These determine only how the celestial pole is to be located, but not how velocities are to be referenced. specific pos-vel coordinates are referenced to an 'astro_frame', which must specify one of the values defined here.

See also: novas_frame; NOVAS_REFERENCE_SYSTEMS

Enumerator NOVAS_GCRS

Geocentric Celestial Reference system. Essentially the same as ICRS but includes aberration and gravitational deflection for an observer around Earth.

NOVAS_TOD

True equinox Of Date: dynamical system of the 'true' equator, with its origin at the 'true' equinox (pre IAU 2006 system).

NOVAS_CIRS

Celestial Intermediate Reference System: dynamical system of the true equator, with its origin at the CIO (preferred since IAU 2006)

NOVAS_ICRS

International Celestial Reference system. The equatorial system fixed to the frame of distant quasars.

NOVAS_J2000

The J2000 dynamical reference system

Since: 1.1

NOVAS_MOD

Mean equinox of date: dynamical system of the 'mean' equator, with its origin at the 'mean' equinox (pre IAU 2006 system). It includes precession (Lieske et. al. 1977), but no nutation. For example, FK4 / B1950 is a MOD coordinate system.

Since: 1.1

NOVAS_TIRS

Terrestrial Intermediate Reference System. It is the IAU 2006 standard pseudo Earth-fixed (PEF) coordinate system, which co-rotates with Earth, but does not include Earth polar wobble corrections.

Since: 1.4

NOVAS_ITRS

International Terrestrial Reference System. This is the IAU 2006 Earth-fixed reference system, and includes small measured corrections for the unmodelled polar motion, as published by the IERS Bulletins.

Since: 1.4

◆ novas_refraction_model

Constants that determine whether what model (if any) to use for implicit refraction calculations.

See also: on_surface; refract(); refract_astro()

Enumerator NOVAS_NO_ATMOSPHERE

Do not apply atmospheric refraction correction.

NOVAS_STANDARD_ATMOSPHERE

Uses a standard atmospheric model, ignoring all weather values defined for the specific observing location

NOVAS_WEATHER_AT_LOCATION

Uses the weather parameters that are specified together with the observing location.

NOVAS_RADIO_REFRACTION

Uses the Berman & Rockwell 1976 refraction model for Radio wavelengths with the weather parameters specified together with the observing location.

Since: 1.4

NOVAS_WAVE_REFRACTION

Uses the IAU / SOFA wavelength-depended refraction model with the weather parameters specified together with the observing location. The wavelength can be specified via novas_refract_wavelength() or else it is assumed to be 550 nm (visible light).

See also: novas_refract_wavelength()

Since: 1.4

◆ novas_refraction_type

The type of elevation value for which to calculate a refraction.

See also: RefractionModel

Since: 1.1

Enumerator NOVAS_REFRACT_OBSERVED

Refract observed elevation value.

NOVAS_REFRACT_ASTROMETRIC

Refract astrometric elevation value.

◆ novas_separator_type

Separator type to use for broken-down time/angle string representations in HMS/DMS formats.

Since: 1.3

See also: novas_print_hms(); novas_print_dms()

Enumerator NOVAS_SEP_COLONS

Use colons between components, e.g. '12:34:56'.

NOVAS_SEP_SPACES

Use spaces between components, e.g. '12 34 56'.

NOVAS_SEP_UNITS

Use unit markers after each component, e.g. '12h34m56s'.

NOVAS_SEP_UNITS_AND_SPACES

Useunit markers after each compoent, plus spaces between components, e.g. '12h 34m 56s'.

◆ novas_timescale

Constants to reference various astrnomical timescales used

See also: NOVAS_TIMESCALES; timescale.c

Since: 1.1

Enumerator NOVAS_TCB

Barycentric Coordinate Time (TCB)

NOVAS_TDB

Barycentric Dynamical Time (TDB)

NOVAS_TCG

Geocentric Coordinate Time (TCG)

NOVAS_TT

Terrestrial Time (TT)

NOVAS_TAI

Innternational Atomic Time (TAI)

NOVAS_GPS

GPS Time.

NOVAS_UTC

Universal Coordinated Time (UTC)

NOVAS_UT1

UT1 earth rotation time, based on the measured Earth orientation parameters published in IERS Bulletin A.

◆ novas_transform_type

The types of coordinate transformations available for tranform_cat().

See also: transform_cat(); NOVAS_TRANSFORM_TYPES

Enumerator PROPER_MOTION

Updates the star's data to account for the star's space motion between the first and second dates, within a fixed reference frame.

PRECESSION

applies a rotation of the reference frame corresponding to precession between the first and second dates, but leaves the star fixed in space.

CHANGE_EPOCH

The combined equivalent of PROPER_MOTION and PRECESSION together.

CHANGE_J2000_TO_ICRS

A fixed rotation about very small angles (<0.1 arcsecond) to take data from the dynamical system of J2000.0 to the ICRS.

CHANGE_ICRS_TO_J2000

The inverse transformation of J2000_TO_ICRS.

◆ novas_wobble_direction

Direction constants for polar wobble corrections via the wobble() function.

See also: wobble(); NOVAS_WOBBLE_DIRECTIONS

Enumerator WOBBLE_ITRS_TO_TIRS

use for wobble() to change from ITRS (Earth-fixed) to TIRS (pseudo Earth-fixed). It includes TIO longitude correction.

Since: 1.4

WOBBLE_TIRS_TO_ITRS

use for wobble() to change from TIRS (pseudo Earth-fixed) to ITRS (Earth-fixed). It includes TIO longitude correction.

Since: 1.4

WOBBLE_ITRS_TO_PEF

use for wobble() to change from ITRS (Earth-fixed) Pseudo Earth Fixed (PEF). It does not include TIO longitude correction. Otherwise, it's the same as WOBBLE_ITRS_TO_TIRS

WOBBLE_PEF_TO_ITRS

use for wobble() to change from Pseudo Earth Fixed (PEF) to ITRS (Earth-fixed). It does not include TIO longitude correction. Otherwise, it's the same as WOBBLE_TIRS_TO_ITRS

◆ aberration() int aberration ( const double * pos, const double * vobs, double lighttime, double * out )

Corrects position vector for aberration of light. Algorithm includes relativistic terms.

NOTES:

This function is called by place() to account for aberration when calculating the position of the source.

REFERENCES:

Murray, C. A. (1981) Mon. Notices Royal Ast. Society 195, 639-648.
Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: pos [AU] Position vector of source relative to observer vobs [AU/day] Velocity vector of observer, relative to the solar system barycenter, components in AU/day. lighttime [day] Light time from object to Earth in days (if known). Or set to 0, and this function will compute it. [out] out [AU] Position vector, referred to origin at center of mass of the Earth, corrected for aberration, components in AU. It can be the same vector as one of the inputs.

Returns: 0 if successful, or -1 if any of the vector arguments are NULL.

See also: place()

References novas_vlen().

◆ accum_prec() double accum_prec ( double t )

Returns the general precession in longitude (Simon et al. 1994), equivalent to 5028.8200 arcsec/cy at J2000.

Parameters: t [cy] Julian centuries since J2000

Returns: [rad] the approximate precession angle [-π:π].

See also: planet_lon(); nutation_angles(); ee_ct(); NOVAS_JD_J2000

Since: 1.0

Author: Attila Kovacs

References TWOPI.

◆ app_planet() short app_planet ( double jd_tt, const object *restrict ss_body, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis )

Computes the apparent place of a solar system body. This is the same as calling place() for the body with NOVAS_TOD as the system, except the different set of return values used.

NOTES:

This call uses the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C function.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Deprecated:: Use place_cirs() is now preferred, especially for high accuracy calculations.

Parameters: jd_tt [day] Terretrial Time (TT) based Julian date. ss_body Pointer to structure containing the body designation for the solar system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Apparent right ascension in hours, referred to true equator and equinox of date 'jd_tt'. (It may be NULL if not required) [out] dec [deg] Apparent declination in degrees, referred to true equator and equinox of date 'jd_tt'. (It may be NULL if not required) [out] dis [AU] True distance from Earth to the body at 'jd_tt' in AU (can be NULL if not needed).

Returns: 0 if successful, or -1 if the object argument is NULL, or else 1 if the value of 'type' in structure 'ss_body' is invalid, or 10 + the error code from place().

See also: place_tod(); astro_planet(); local_planet(); topo_planet(); virtual_planet(); app_star()

References NOVAS_TOD, and radec_planet().

◆ app_star() short app_star ( double jd_tt, const cat_entry *restrict star, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec )

Computes the apparent place of a star, referenced to dynamical equator at date 'jd_tt', given its catalog mean place, proper motion, parallax, and radial velocity.

Notwithstanding the different set of return values, this is the same as calling place_star() with a NULL observer location and NOVAS_TOD as the system for an object that specifies the star.

NOTES:

This call uses the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C function.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992), Chapter 3.

Deprecated:: Use place_cirs() is now preferred, especially for high accuracy calculations.

Parameters: jd_tt [day] Terretrial Time (TT) based Julian date. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Apparent right ascension in hours, referred to true equator and equinox of date 'jd_tt' (it may be NULL if not required). [out] dec [deg] Apparent declination in degrees, referred to true equator and equinox of date 'jd_tt' (it may be NULL if not required).

Returns: 0 if successful, -1 if a required pointer argument is NULL, or else an the error from make_object(), or 20 + the error from place().

See also: place_tod(); place_star(); astro_star(); local_star(); topo_star(); virtual_star(); app_planet()

References NOVAS_TOD, and radec_star().

◆ app_to_cirs_ra() double app_to_cirs_ra ( double jd_tt, enum novas_accuracy accuracy, double ra )

Converts an apparent right ascension coordinate (measured from the true equinox of date) to a CIRS R.A., measured from the CIO.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) ra [h] the apparent R.A. coordinate measured from the true equinox of date.

Returns: [h] The CIRS right ascension coordinate, measured from the CIO [0:24], or NAN if the accuracy is invalid, or if there wan an error from cio_ra().

See also: cirs_to_app_ra(); tod_to_cirs()

Since: 1.0.1

Author: Attila Kovacs

References cio_ra().

◆ astro_planet() short astro_planet ( double jd_tt, const object *restrict ss_body, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis )

Computes the astrometric place of a solar system body, referenced to the ICRS without light deflection or aberration. This is the same as calling place_icrs() for the body, except the different set of return values used.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Parameters: jd_tt [day] Terretrial Time (TT) based Julian date. ss_body Pointer to structure containing the body designation for the solar system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Astrometric right ascension in hours, referred to the ICRS, without light deflection or aberration. (It may be NULL if not required) [out] dec [deg] Astrometric declination in degrees, referred to the ICRS, without light deflection or aberration. (It may be NULL if not required) [out] dis [AU] True distance from Earth to the body at 'jd_tt' in AU (can be NULL if not needed).

Returns: 0 if successful, or -1 if the object is NULL, or else 1 if the value of 'type' in structure 'ss_body' is invalid, or 10 + the error code from place().

See also: place_icrs(); app_planet(); local_planet(); topo_planet(); virtual_planet(); astro_star()

References NOVAS_ICRS, and radec_planet().

◆ astro_star() short astro_star ( double jd_tt, const cat_entry *restrict star, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec )

Computes the astrometric place of a star, referred to the ICRS without light deflection or aberration, at date 'jd_tt', given its catalog mean place, proper motion, parallax, and radial velocity.

Notwithstanding the different set of return values, this is the same as calling place_star() with a NULL observer location and NOVAS_ICRS as the system, or place_icrs() for an object that specifies the star.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992), Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Astrometric right ascension in hours, referred to the ICRS, without light deflection or aberration. (It may be NULL if not required) [out] dec [deg] Astrometric declination in degrees, referred to the ICRS, without light deflection or aberration. (It may be NULL if not required)

Returns: 0 if successful, or -1 if a required pointer argument is NULL, or 20 + the error from place().

See also: place_star(); place_icrs(); app_star(); local_star(); topo_star(); virtual_star(); astro_planet()

References NOVAS_ICRS, and radec_star().

◆ bary2obs() int bary2obs ( const double * pos, const double * pos_obs, double * out, double *restrict lighttime )

Moves the origin of coordinates from the barycenter of the solar system to the observer (or the geocenter); i.e., this function accounts for parallax (annual+geocentric or just annual).

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: pos [AU] Position vector, referred to origin at solar system barycenter, components in AU. pos_obs [AU] Position vector of observer (or the geocenter), with respect to origin at solar system barycenter, components in AU. [out] out [AU] Position vector, referred to origin at center of mass of the Earth, components in AU. It may be NULL if not required, or be the same vector as either of the inputs. [out] lighttime [day] Light time from object to Earth in days. It may be NULL if not required.

Returns: 0 if successful, or -1 if any of the essential pointer arguments is NULL.

See also: place(); light_time2()

References novas_vlen().

◆ cal_date() int cal_date ( double tjd, short *restrict year, short *restrict month, short *restrict day, double *restrict hour )

This function will compute a broken down date on the astronomical calendar for given the Julian day input. Input Julian day can be based on any UT-like time scale (UTC, UT1, TT, etc.) - output time value will have same basis.

NOTES:

The Gregorian calendar was introduced on 15 October 1582 only (corresponding to 5 October of the previously used Julian calendar). Prior to it this function returns Julian/Roman calendar dates, e.g. the day before the reform is 1582 October 4. You can use novas_id_to_calendar() instead to convert JD days to dates in specific calendars.
B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

REFERENCES:

Fliegel, H. & Van Flandern, T. Comm. of the ACM, Vol. 11, No. 10, October 1968, p. 657.15 October 1582

Parameters: tjd [day] Julian date [out] year [yr] Astronomical calendar year. It may be NULL if not required. B.C. years are represented as <=0, i.e. 1 B.C. as 0 and X B.C. as (1 - X) [out] month [month] Astronomical calendar month [1:12]. It may be NULL if not required. [out] day [day] Day of the month [1:31]. It may be NULL if not required. [out] hour [h] Hour of day [0:24]. It may be NULL if not required.

Returns: 0

See also: novas_jd_to_date(); novas_jd_from_date(); get_utc_to_tt(); get_ut1_to_tt(); tt2tdb()

References NOVAS_ASTRONOMICAL_CALENDAR, and novas_jd_to_date().

◆ cel2ter()

Rotates a vector from the celestial to the terrestrial system. Specifically, it transforms a vector in the GCRS, or the dynamcal CIRS or TOD frames to the ITRS (a rotating earth-fixed system) by applying rotations for the GCRS-to-dynamical frame tie, precession, nutation, Earth rotation, and polar motion.

If 'system' is NOVAS_CIRS then method EROT_ERA must be used. Similarly, if 'system' is NOVAS_TOD then method must be EROT_ERA. Otherwise an error 3 is returned.

If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.

Deprecated:: This function can be confusing to use due to the input coordinate system being specified by a combination of two options. Use itrs_to_cirs() or itrs_to_tod() instead. You can then follow these with other conversions to GCRS (or whatever else) as appropriate.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Kaplan, G. H. (2003), 'Another Look at Non-Rotating Origins', Proceedings of IAU XXV J oint Discussion 16.

Parameters: jd_ut1_high [day] High-order part of UT1 Julian date. jd_ut1_low [day] Low-order part of UT1 Julian date. ut1_to_tt [s] TT - UT1 Time difference in seconds erot EROT_ERA (0) or EROT_GST (1), depending on whether to use GST relative to equinox of date (pre IAU 2006) or ERA relative to the CIO (IAU 2006 standard) as the Earth rotation measure. The main effect of this option is that it specifies the input coordinate system as CIRS or TOD when the input coordinate class is NOVAS_DYNAMICAL_CLASS. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) coordType Input coordinate class, NOVAS_REFERENCE_CLASS (0) or NOVAS_DYNAMICAL_CLASS (1). Use the former if the input coordinates are in the GCRS, and the latter if they are CIRS or TOD (the 'erot' parameter selects which dynamical system the input is specified in.) xp [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. in Input position vector, geocentric equatorial rectangular coordinates in the specified input coordinate system (GCRS if 'class' is NOVAS_REFERENCE_CLASS; or else either CIRS if 'erot' is EROT_ERA, or TOD if 'erot' is EROT_GST). [out] out ITRS position vector, geocentric equatorial rectangular coordinates (terrestrial system). It can be the same vector as the input.

Returns: 0 if successful, -1 if either of the vector arguments is NULL, 1 if 'accuracy' is invalid, 2 if 'method' is invalid, or else 10 + the error from cio_location(), or 20 + error from cio_basis().

See also: gcrs_to_cirs(); cirs_to_itrs(); frame_tie(); j2000_to_tod(); tod_to_itrs(); ter2cel()

References era(), EROT_ERA, EROT_GST, gcrs_to_cirs(), gcrs_to_tod(), NOVAS_DYNAMICAL_CLASS, NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NOVAS_TRUE_EQUINOX, sidereal_time(), spin(), wobble(), WOBBLE_PEF_TO_ITRS, and WOBBLE_TIRS_TO_ITRS.

◆ cel_pole()

Specifies the unmodeled celestial pole offsets for high-precision applications to be applied to the True of Date (TOD) equator, in the old, pre IAU 2006 methodology. These offsets must not include tidal terms, and should be specified relative to the IAU2006 precession/nutation model to provide a correction to the modeled (precessed and nutated) position of Earth's pole, such those derived from observations and published by IERS.

The call sets the global variables PSI_COR and EPS_COR, for subsequent calls to e_tilt(). As such, it should be called to specify pole offsets prior to legacy NOVAS C equinox-specific calls. The global values of PSI_COR and EPS_COR specified via this function will be effective until explicitly changed again.

NOTES:

The pole offsets et this way will affect all future TOD-based calculations, until the pole is changed or reset again. Hence, you should be extremely careful using it (if at all), as it may become an unpredictable source of inaccuracy if implicitly applied without intent to do so.
The current UT1 - UTC time difference, and polar offsets, historical data and near-term projections are published in the <a href="https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html>IERS Bulletins
If Δδψ, Δδdε offsets are specified, these must be the residual corrections relative to the IAU 2006 precession/nutation model (not the Lieske et al. 1977 model!). As such, they are just a rotated version of the newer dx, dy offsets published by IERS.
The equivalent IAU 2006 standard is to apply dx, dy pole offsets only for converting between TIRS and ITRS, e.g. via wobble()).
There is no need to define pole offsets this way when using the newer frame-based approach introduced in SuperNOVAS. If the pole offsets are specified on a per-frame basis during the initialization of each observing frame, the offsets will be applied for the TIRS / ITRS conversion only, and not to the TOD equator per se.

REFERENCES:

Kaplan, G. (2005), US Naval Observatory Circular 179.
Kaplan, G. (2003), USNO/AA Technical Note 2003-03.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. Used only if 'type' is POLE_OFFSETS_X_Y (2), to transform dx and dy to the equivalent Δδψ and Δδε values. type POLE_OFFSETS_DPSI_DEPS (1) if the offsets are Δδψ, Δδε relative to the IAU 20006 precession/nutation model; or POLE_OFFSETS_X_Y (2) if they are dx, dy offsets relative to the IAU 2000/2006 precession-nutation model. dpole1 [mas] Value of celestial pole offset in first coordinate, (Δδψ for or dx) in milliarcseconds, relative to the IAU2006 precession/nutation model. dpole2 [mas] Value of celestial pole offset in second coordinate, (Δδε or dy) in milliarcseconds, relative to the IAU2006 precession/nutation model.

Returns: 0 if successful, or else 1 if 'type' is invalid.

See also: wobble(); e_tilt(); place(); cirs_to_itrs(); tod_to_itrs(); get_ut1_to_tt(); sidereal_time(); NOVAS_FULL_ACCURACY

Deprecated:: This old way of incorporating Earth orientation parameters into the true equator and equinox is now disfavored. Instead, wobble() should be used to convert between the Terrestrial Intermediate Reference System (TIRS) / Pseudo Earth Fixed (PEF) and the International Terrestrial Reference System (ITRS) going forward.

References POLE_OFFSETS_DPSI_DEPS, and POLE_OFFSETS_X_Y.

◆ cio_array() short cio_array ( double jd_tdb, long n_pts, ra_of_cio *restrict cio )

Given an input TDB Julian date and the number of data points desired, this function returns a set of Julian dates and corresponding values of the GCRS right ascension of the celestial intermediate origin (CIO). The range of dates is centered (at least approximately) on the requested date. The function obtains the data from an external data file.

This function assumes that a CIO locator file (CIO_RA.TXT or cio_ra.bin) exists in the default location (configured at build time), or else was specified via set_cio_locator_file() prior to calling this function.

NOTES:

This function has been completely re-written by A. Kovacs to provide much more efficient caching and I/O.

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date n_pts Number of Julian dates and right ascension values requested (not less than 2 or more than NOVAS_CIO_CACHE_SIZE). [out] cio A time series (array) of the right ascension of the Celestial Intermediate Origin (CIO) with respect to the GCRS.

Returns: 0 if successful, -1 if the output array is NULL or there was an I/O error accessing the CIO location data file. Or else 1 if no locator data file is available, 2 if 'jd_tdb' not in the range of the CIO file, 3 if 'n_pts' out of range, or 6 if 'jd_tdb' is too close to either end of the CIO file do we are unable to put 'n_pts' data points into the output

See also: set_cio_locator_file(); cio_location()

References DEFAULT_CIO_LOCATOR_FILE, NOVAS_CIO_CACHE_SIZE, and set_cio_locator_file().

◆ cio_basis()

Computes the orthonormal basis vectors, with respect to the GCRS (geocentric ICRS), of the celestial intermediate system defined by the celestial intermediate pole (CIP) (in the z direction) and the celestial intermediate origin (CIO) (in the x direction). A TDB Julian date and the right ascension of the CIO at that date is required as input. The right ascension of the CIO can be with respect to either the GCRS origin or the true equinox of date – different algorithms are used in the two cases.

This function effectively constructs the matrix C in eq. (3) of the reference.

NOTES:

This function caches the results of the last calculation in case it may be re-used at no extra computational cost for the next call.

REFERENCES:

Kaplan, G. (2005), US Naval Observatory Circular 179.

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date ra_cio [h] Right ascension of the CIO at epoch (hours). loc_type CIO_VS_GCRS (1) if the cio location is relative to the GCRS or else CIO_VS_EQUINOX (2) if relative to the true equinox of date. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] x Unit 3-vector toward the CIO, equatorial rectangular coordinates, referred to the GCRS. [out] y Unit 3-vector toward the y-direction, equatorial rectangular coordinates, referred to the GCRS. [out] z Unit 3-vector toward north celestial pole (CIP), equatorial rectangular coordinates, referred to the GCRS.

Returns: 0 if successful, or -1 if any of the output vector arguments are NULL or if the accuracy is invalid, or else 1 if 'ref-sys' is invalid.

See also: cio_location(); gcrs_to_cirs()

References CIO_VS_EQUINOX, CIO_VS_GCRS, NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, novas_vlen(), and tod_to_gcrs().

◆ cio_location() short cio_location ( double jd_tdb, enum novas_accuracy accuracy, double *restrict ra_cio, short *restrict loc_type )

Returns the location of the celestial intermediate origin (CIO) for a given Julian date, as a right ascension with respect to either the GCRS (geocentric ICRS) origin or the true equinox of date. The CIO is always located on the true equator (= intermediate equator) of date.

The user may specify an interpolation file to use via set_cio_locator_file() prior to calling this function. In that case the call will return CIO location relative to GCRS. In the absence of the table, it will calculate the CIO location relative to the true equinox. In either case the type of the location is returned alongside the corresponding CIO location value.

NOTES:

Unlike the NOVAS C version of this function, this version will always return a CIO location as long as the pointer arguments are not NULL. The returned values will be interpolated from the locator file if possible, otherwise it falls back to calculating an equinox-based location per default.
This function caches the results of the last calculation in case it may be re-used at no extra computational cost for the next call.

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra_cio [h] Right ascension of the CIO, in hours, or NAN if returning with an error. [out] loc_type Pointer in which to return the reference system in which right ascension is given, which is either CIO_VS_GCRS (1) if the location was obtained via interpolation of the available data file, or else CIO_VS_EQUINOX (2) if it was calculated locally. It is set to -1 if returning with an error.

Returns: 0 if successful, -1 if one of the pointer arguments is NULL or the accuracy is invalid.

See also: set_cio_locator_file(); cio_ra(); gcrs_to_cirs()

References cio_array(), CIO_VS_EQUINOX, CIO_VS_GCRS, ira_equinox(), novas_debug(), NOVAS_DEBUG_OFF, NOVAS_DEBUG_ON, NOVAS_FULL_ACCURACY, novas_get_debug_mode(), NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUINOX.

◆ cio_ra() short cio_ra ( double jd_tt, enum novas_accuracy accuracy, double *restrict ra_cio )

Computes the true right ascension of the celestial intermediate origin (CIO) at a given TT Julian date. This is the negative value for the equation of the origins.

REFERENCES:

Kaplan, G. (2005), US Naval Observatory Circular 179.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra_cio [h] Right ascension of the CIO, with respect to the true equinox of date, in hours (+ or -), or NAN when returning with an error code.

Returns: 0 if successful, -1 if the output pointer argument is NULL, 1 if 'accuracy' is invalid, 10–20: 10 + error code from cio_location(), or else 20 + error from cio_basis()

References cio_basis(), cio_location(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and tod_to_gcrs().

◆ cirs_to_app_ra() double cirs_to_app_ra ( double jd_tt, enum novas_accuracy accuracy, double ra )

Converts a CIRS right ascension coordinate (measured from the CIO) to an apparent R.A. measured from the true equinox of date.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) ra [h] The CIRS right ascension coordinate, measured from the CIO.

Returns: [h] the apparent R.A. coordinate measured from the true equinox of date [0:24], or NAN if the accuracy is invalid, or if there wan an error from cio_ra().

See also: app_to_cirs_ra(); cirs_to_tod()

Since: 1.0.1

Author: Attila Kovacs

References cio_ra().

◆ cirs_to_gcrs() int cirs_to_gcrs ( double jd_tdb, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from the Celestial Intermediate Reference System (CIRS) frame at the given epoch to the Geocentric Celestial Reference System (GCRS).

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in CIRS Input (x, y, z) position or velocity vector [out] out Output position or velocity 3-vector in the GCRS coordinate frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL or the accuracy is invalid, or an error from cio_location(), or else 10 + the error from cio_basis().

See also: tod_to_gcrs(); gcrs_to_cirs(); cirs_to_itrs(); cirs_to_tod()

Since: 1.0

Author: Attila Kovacs

References cio_basis(), and cio_location().

◆ cirs_to_itrs() int cirs_to_itrs ( double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double * in, double * out )

Rotates a position vector from the dynamical CIRS frame of date to the Earth-fixed ITRS frame (IAU 2000 standard method).

If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.

If extreme (sub-microarcsecond) accuracy is not required, you can use UT1-based Julian date instead of the TT-based Julian date and set the 'ut1_to_tt' argument to 0.0. and you can use UTC-based Julian date the same way.for arcsec-level precision also.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Kaplan, G. H. (2003), 'Another Look at Non-Rotating Origins', Proceedings of IAU XXV Joint Discussion 16.

Parameters: jd_tt_high [day] High-order part of Terrestrial Time (TT) based Julian date. jd_tt_low [day] Low-order part of Terrestrial Time (TT) based Julian date. ut1_to_tt [s] TT - UT1 Time difference in seconds accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) xp [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. in Position vector, geocentric equatorial rectangular coordinates, referred to CIRS axes (celestial system). [out] out Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system).

Returns: 0 if successful, -1 if either of the vector arguments is NULL, 1 if 'accuracy' is invalid, 2 if 'method' is invalid 10–20, 3 if the method and option are mutually incompatible, or else 10 + the error from cio_location(), or 20 + error from cio_basis().

See also: tod_to_itrs(); itrs_to_cirs(); gcrs_to_cirs(); cirs_to_gcrs(); cirs_to_tod()

Since: 1.0

Author: Attila Kovacs

References cel2ter(), EROT_ERA, and NOVAS_DYNAMICAL_CLASS.

◆ cirs_to_tod() int cirs_to_tod ( double jd_tt, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from the Celestial Intermediate Reference System (CIRS) at the given epoch to the True of Date (TOD) reference system.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in CIRS Input (x, y, z) position or velocity vector [out] out Output position or velocity 3-vector in the True of Date (TOD) frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL or the accuracy is invalid, or 10 + the error from cio_location(), or else 20 + the error from cio_basis().

See also: tod_to_cirs(); cirs_to_app_ra(); cirs_to_gcrs(); cirs_to_itrs()

Since: 1.1

Author: Attila Kovacs

References cio_ra(), and spin().

◆ d_light() double d_light ( const double * pos_src, const double * pos_body )

Returns the difference in light-time, for a star, between the barycenter of the solar system and the observer (or the geocenter) (Usage A).

Alternatively (Usage B), this function returns the light-time from the observer (or the geocenter) to a point on a light ray that is closest to a specific solar system body. For this purpose, 'pos_src' is the position vector toward observed object, with respect to origin at observer (or the geocenter); 'pos_body' is the position vector of solar system body, with respect to origin at observer (or the geocenter), components in AU; and the returned value is the light time to point on line defined by 'pos' that is closest to solar system body (positive if light passes body before hitting observer, i.e., if 'pos_body' is within 90 degrees of 'pos_src').

NOTES:

This function is called by place()

Parameters: pos_src Position vector towards observed object, with respect to the SSB (Usage A), or relative to the observer / geocenter (Usage B). pos_body [AU] Position of observer relative to SSB (Usage A), or position of intermediate solar-system body with respect to the observer / geocenter (Usage B).

Returns: [day] Difference in light time to observer, either relative to SSB (Usage A) or relative intermediate solar-system body (Usage B); or else NAN if either of the input arguments is NULL.

See also: place()

References novas_vlen().

◆ e_tilt() int e_tilt ( double jd_tdb, enum novas_accuracy accuracy, double *restrict mobl, double *restrict tobl, double *restrict ee, double *restrict dpsi, double *restrict deps )

Computes quantities related to the orientation of the Earth's rotation axis at the specified Julian date.

Unmodelled corrections to earth orientation can be defined via cel_pole() prior to this call.

NOTES:

This function caches the results of the last calculation in case it may be re-used at no extra computational cost for the next call.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] mobl [deg] Mean obliquity of the ecliptic. It may be NULL if not required. [out] tobl [deg] True obliquity of the ecliptic. It may be NULL if not required. [out] ee [s] Equation of the equinoxes in seconds of time. It may be NULL if not required. [out] dpsi [arcsec] Nutation in longitude. It may be NULL if not required. [out] deps [arcsec] Nutation in obliquity. It may be NULL if not required.

Returns: 0 if successful, or -1 if the accuracy argument is invalid

See also: cel_pole(); place(); equ2ecl(); ecl2equ()

References ee_ct(), mean_obliq(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and nutation_angles().

◆ ecl2equ() int ecl2equ ( double jd_tt, enum novas_equator_type coord_sys, enum novas_accuracy accuracy, double elon, double elat, double *restrict ra, double *restrict dec )

Convert ecliptic longitude and latitude to right ascension and declination. To convert GCRS ecliptic coordinates (mean ecliptic and equinox of J2000.0), set 'coord_sys' to NOVAS_GCRS_EQUATOR(2); in this case the value of 'jd_tt' can be set to anything, since J2000.0 is assumed. Otherwise, all input coordinates are dynamical at'jd_tt'.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. (Unused if 'coord_sys' is NOVAS_GCRS_EQUATOR[2]) coord_sys The astrometric reference system of the coordinates. If 'coord_sys' is NOVAS_GCRS_EQUATOR(2), the input GCRS coordinates are converted to J2000 ecliptic coordinates. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) elon [deg] Ecliptic longitude in degrees, referred to specified ecliptic and equinox of date. elat [deg] Ecliptic latitude in degrees, referred to specified ecliptic and equinox of date. [out] ra [h] Right ascension in hours, referred to specified equator and equinox of date. [out] dec [deg] Declination in degrees, referred to specified equator and equinox of date.

Returns: 0 if successful, or else 1 if the value of 'coord_sys' is invalid.

See also: ecl2equ_vec(); equ2ecl()

Since: 1.0

Author: Attila Kovacs

References ecl2equ_vec().

◆ ecl2equ_vec()

Converts an ecliptic position vector to an equatorial position vector. To convert ecliptic coordinates (mean ecliptic and equinox of J2000.0) to GCRS RA and dec to, set 'coord_sys' to NOVAS_GCRS_EQUATOR(2); in this case the value of 'jd_tt' can be set to anything, since J2000.0 is assumed. Otherwise, all input coordinates are dynamical at 'jd_tt'.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. (Unused if 'coord_sys' is NOVAS_GCRS_EQUATOR[2]) coord_sys The astrometric reference system type of the coordinates accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in Position vector, referred to specified ecliptic and equinox of date. [out] out Position vector, referred to specified equator and equinox of date. It can be the same vector as the input.

Returns: 0 if successful, -1 if either vector argument is NULL or the accuracy is invalid, or else 1 if the value of 'coord_sys' is invalid.

See also: ecl2equ(); equ2ecl_vec()

References e_tilt(), frame_tie(), J2000_TO_ICRS, mean_obliq(), NOVAS_FULL_ACCURACY, NOVAS_GCRS_EQUATOR, NOVAS_MEAN_EQUATOR, NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUATOR.

◆ ee_ct() double ee_ct ( double jd_tt_high, double jd_tt_low, enum novas_accuracy accuracy )

Computes the "complementary terms" of the equation of the equinoxes. The input Julian date can be split into high and low order parts for improved accuracy. Typically, the split is into integer and fractiona parts. If the precision of a single part is sufficient, you may set the low order part to 0.

The series used in this function was derived from the first reference. This same series was also adopted for use in the IAU's Standards of Fundamental Astronomy (SOFA) software (i.e., subroutine eect00.for and function eect00.c).

The low-accuracy series used in this function is a simple implementation derived from the first reference, in which terms smaller than 2 microarcseconds have been omitted.

NOTES:

This function caches the results of the last calculation in case it may be re-used at no extra computational cost for the next call.

REFERENCES:

Capitaine, N., Wallace, P.T., and McCarthy, D.D. (2003). Astron. & Astrophys. 406, p. 1135-1149. Table 3.
IERS Conventions (2010), Chapter 5, p. 60, Table 5.2e.
(Table 5.2e presented in the printed publication is a truncated series. The full series, which is used in NOVAS, is available on the IERS Conventions Center website: ftp://tai.bipm.org/iers/conv2010/chapter5/tab5.2e.txt)

Parameters: jd_tt_high [day] High-order part of TT based Julian date. jd_tt_low [day] Low-order part of TT based Julian date. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1)

Returns: [rad] Complementary terms, in radians.

See also: e_tilt(); cel_pole(); nutation(); sidereal_time()

Deprecated:: (for intrernal use) There is no good reason why this function should be exposed to users of the library. It is intended only for use by e_tilt() internally.

References accum_prec(), novas_delaunay_args::D, novas_delaunay_args::F, fund_args(), NOVAS_FULL_ACCURACY, NOVAS_MERCURY, NOVAS_NEPTUNE, NOVAS_REDUCED_ACCURACY, novas_delaunay_args::Omega, and planet_lon().

◆ ephemeris() short ephemeris ( const double *restrict jd_tdb, const object *restrict body, enum novas_origin origin, enum novas_accuracy accuracy, double *restrict pos, double *restrict vel )

Retrieves the position and velocity of a solar system body from a fundamental ephemeris.

It is recommended that the input structure 'cel_obj' be created using make_object()

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date body Pointer to structure containing the designation of the body of interest origin NOVAS_BARYCENTER (0) or NOVAS_HELIOCENTER (1) accuracy NOCAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos [AU] Pointer to structure containing the designation of the body of interest [out] vel [AU/day] Velocity vector of the body at 'jd_tdb'; equatorial rectangular coordinates in AU/day referred to the ICRS.

Returns: 0 if successful, -1 if the 'jd_tdb' or input object argument is NULL, or else 1 if 'origin' is invalid, 2 if cel_obj->type is invalid, 10 + the error code from solarsystem(), or 20 + the error code from readeph().

See also: set_planet_provider(); set_planet_provider_hp(); set_ephem_provider(); ephem_open(); make_planet(); make_ephem_object()

References ephemeris(), get_ephem_provider(), make_planet(), NOVAS_BARYCENTER, NOVAS_EPHEM_OBJECT, NOVAS_FULL_ACCURACY, NOVAS_HELIOCENTER, novas_orbit_posvel(), NOVAS_ORBITAL_OBJECT, NOVAS_ORIGIN_TYPES, NOVAS_PLANET, NOVAS_SSB, NOVAS_SUN, and readeph().

◆ equ2ecl() short equ2ecl ( double jd_tt, enum novas_equator_type coord_sys, enum novas_accuracy accuracy, double ra, double dec, double *restrict elon, double *restrict elat )

Convert right ascension and declination to ecliptic longitude and latitude. To convert GCRS RA and dec to ecliptic coordinates (mean ecliptic and equinox of J2000.0), set 'coord_sys' to NOVAS_GCRS_EQUATOR(2); in this case the value of 'jd_tt' can be set to anything, since J2000.0 is assumed. Otherwise, all input coordinates are dynamical at 'jd_tt'.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. (Unused if 'coord_sys' is NOVAS_GCRS_EQUATOR[2]) coord_sys The astrometric reference system of the coordinates. If 'coord_sys' is NOVAS_GCRS_EQUATOR(2), the input GCRS coordinates are converted to J2000 ecliptic coordinates. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) ra [h] Right ascension in hours, referred to specified equator and equinox of date. dec [deg] Declination in degrees, referred to specified equator and equinox of date. [out] elon [deg] Ecliptic longitude in degrees, referred to specified ecliptic and equinox of date. [out] elat [deg] Ecliptic latitude in degrees, referred to specified ecliptic and equinox of date.

Returns: 0 if successful, or else 1 if the value of 'coord_sys' is invalid.

See also: equ2ecl_vec(); ecl2equ()

References equ2ecl_vec().

◆ equ2ecl_vec()

Converts an equatorial position vector to an ecliptic position vector. To convert ICRS RA and dec to ecliptic coordinates (mean ecliptic and equinox of J2000.0), set 'coord_sys' to NOVAS_GCRS_EQUATOR(2); in this case the value of 'jd_tt' can be set to anything, since J2000.0 is assumed. Otherwise, all input coordinates are dynamical at 'jd_tt'.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. (Unused if 'coord_sys' is NOVAS_GCRS_EQUATOR[2]) coord_sys The astrometric reference system type of the coordinates. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in Position vector, referred to specified equator and equinox of date. [out] out Position vector, referred to specified ecliptic and equinox of date. It can be the same vector as the input. If 'coord_sys' is NOVAS_GCRS_EQUATOR(2), the input GCRS coordinates are converted to J2000 ecliptic coordinates.

Returns: 0 if successful, -1 if either vector argument is NULL or the accuracy is invalid, or else 1 if the value of 'coord_sys' is invalid.

See also: equ2ecl(); ecl2equ_vec()

References e_tilt(), frame_tie(), ICRS_TO_J2000, mean_obliq(), NOVAS_FULL_ACCURACY, NOVAS_GCRS_EQUATOR, NOVAS_MEAN_EQUATOR, NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUATOR.

◆ equ2gal() int equ2gal ( double ra, double dec, double *restrict glon, double *restrict glat )

Converts ICRS right ascension and declination to galactic longitude and latitude.

REFERENCES:

Hipparcos and Tycho Catalogues, Vol. 1, Section 1.5.3.

Parameters: ra [h] ICRS right ascension in hours. dec [deg] ICRS declination in degrees. [out] glon [deg] Galactic longitude in degrees. [out] glat [deg] Galactic latitude in degrees.

Returns: 0 if successful, or -1 if either of the output pointer arguments are NULL.

See also: gal2equ()

◆ equ2hor() int equ2hor ( double jd_ut1, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const on_surface *restrict location, double ra, double dec, enum novas_refraction_model ref_option, double *restrict zd, double *restrict az, double *restrict rar, double *restrict decr )

Transforms topocentric (TOD) right ascension and declination to zenith distance and azimuth. This method should not be used to convert CIRS apparent coordinates (IAU 2000 standard) – for those you should use cirs_to_itrs() followed by itrs_to_hor() instead.

It uses a method that properly accounts for polar motion, which is significant at the sub-arcsecond level. This function can also adjust coordinates for atmospheric refraction.

Deprecated:: The name of this function does not reveal what type of equatorial coordinates it requires. To make it less ambiguous, you should use tod_to_itrs() followed by itrs_to_hor() instead, possibly following it with refract_astro() if you also want to apply optical refraction.

NOTES:

'xp' and 'yp' can be set to zero if sub-arcsecond accuracy is not needed.
The directions 'zd'= 0 (zenith) and 'az'= 0 (north) are here considered fixed in the terrestrial system. Specifically, the zenith is along the geodetic normal, and north is toward the ITRS pole.
If 'ref_option' is NOVAS_STANDARD_ATMOSPHERE (1), then 'rar'='ra' and 'decr'='dec'.

REFERENCES:

Kaplan, G. (2008). USNO/AA Technical Note of 28 Apr 2008, "Refraction as a Vector."

Parameters: jd_ut1 [day] UT1 based Julian date ut1_to_tt [s] TT - UT1 Time difference in seconds accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) xp [arcsec] Conventionally-defined x coordinate of celestial intermediate pole with respect to ITRS reference pole, in arcseconds. yp [arcsec] Conventionally-defined y coordinate of celestial intermediate pole with respect to ITRS reference pole, in arcseconds. location The observer location ra [h] Topocentric right ascension of object of interest, in hours, referred to true equator and equinox of date. dec [deg] Topocentric declination of object of interest, in degrees, referred to true equator and equinox of date. ref_option NOVAS_STANDARD_ATMOSPHERE (1), or NOVAS_WEATHER_AT_LOCATION (2) if to use the weather [out] zd [deg] Topocentric zenith distance in degrees (unrefracted). [out] az [deg] Topocentric azimuth (measured east from north) in degrees. [out] rar [h] Topocentric right ascension of object of interest, in hours, referred to true equator and equinox of date, affected by refraction if 'ref_option' is non-zero. (It may be NULL if not required) [out] decr [deg] Topocentric declination of object of interest, in degrees, referred to true equator and equinox of date. (It may be NULL if not required)

Returns: 0 if successful, or -1 if one of the 'zd' or 'az' output pointers are NULL.

See also: itrs_to_hor(); tod_to_itrs(); NOVAS_TOD

References EROT_GST, NOVAS_DYNAMICAL_CLASS, refract_astro(), and ter2cel().

◆ era() double era ( double jd_ut1_high, double jd_ut1_low )

Returns the value of the Earth Rotation Angle (theta) for a given UT1 Julian date. The expression used is taken from the note to IAU Resolution B1.8 of 2000. The input Julian date cane be split into an into high and low order parts (e.g. integer and fractional parts) for improved accuracy, or else one of the components (e.g. the low part) can be set to zero if no split is desired.

The algorithm used here is equivalent to the canonical theta = 0.7790572732640 + 1.00273781191135448 * t, where t is the time in days from J2000 (t = jd_high + jd_low - JD_J2000), but it avoids many two-PI 'wraps' that decrease precision (adopted from SOFA Fortran routine iau_era00; see also expression at top of page 35 of IERS Conventions (1996)).

REFERENCES:

IAU Resolution B1.8, adopted at the 2000 IAU General Assembly, Manchester, UK.
Kaplan, G. (2005), US Naval Observatory Circular 179.

Parameters: jd_ut1_high [day] High-order part of UT1 Julian date. jd_ut1_low [day] Low-order part of UT1 Julian date.

Returns: [deg] The Earth Rotation Angle (theta) in degrees [0:360].

See also: sidereal_time(); cirs_to_itrs(); itrs_to_cirs()

◆ frame_tie()

Transforms a vector from the dynamical reference system to the International Celestial Reference System (ICRS), or vice versa. The dynamical reference system is based on the dynamical mean equator and equinox of J2000.0. The ICRS is based on the space-fixed ICRS axes defined by the radio catalog positions of several hundred extragalactic objects.

For geocentric coordinates, the same transformation is used between the dynamical reference system and the GCRS.

NOTES:

More efficient 3D rotation implementation for small angles by A. Kovacs

REFERENCES:

Hilton, J. and Hohenkerk, C. (2004), Astronomy and Astrophysics 413, 765-770, eq. (6) and (8).
IERS (2003) Conventions, Chapter 5.

Parameters: in Position vector, equatorial rectangular coordinates. direction <0 for for dynamical to ICRS transformation, or else >=0 for ICRS to dynamical transformation. Alternatively you may use the constants J2000_TO_ICRS (-1; or negative) or ICRS_TO_J2000 (0; or positive). [out] out Position vector, equatorial rectangular coordinates. It can be the same vector as the input.

Returns: 0 if successfor or -1 if either of the vector arguments is NULL.

See also: j2000_to_gcrs(); gcrs_to_j2000(); tod_to_j2000(); j2000_to_tod(); j2000_to_gcrs()

◆ fund_args()

Compute the fundamental arguments (mean elements) of the Sun and Moon.

REFERENCES:

Simon et al. (1994) Astronomy and Astrophysics 282, 663-683, esp. Sections 3.4-3.5.

Parameters: t [cy] TDB time in Julian centuries since J2000.0 [out] a [rad] Fundamental arguments data to populate (5 doubles) [0:2π]

Returns: 0 if successful, or -1 if the output pointer argument is NULL.

See also: nutation_angles(); ee_ct(); NOVAS_JD_J2000

References novas_norm_ang().

◆ gal2equ() int gal2equ ( double glon, double glat, double *restrict ra, double *restrict dec )

Converts galactic longitude and latitude to ICRS right ascension and declination.

REFERENCES:

Hipparcos and Tycho Catalogues, Vol. 1, Section 1.5.3.

Parameters: glon [deg] Galactic longitude in degrees. glat [deg] Galactic latitude in degrees. [out] ra [h] ICRS right ascension in hours. [out] dec [deg] ICRS declination in degrees.

Returns: 0 if successful, or -1 if either of the output pointer arguments are NULL.

See also: equ2gal()

Since: 1.0

Author: Attila Kovacs

◆ gcrs2equ()

Converts GCRS right ascension and declination to coordinates with respect to the equator of date (mean or true). For coordinates with respect to the true equator of date, the origin of right ascension can be either the true equinox or the celestial intermediate origin (CIO). This function only supports the CIO-based method.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. (Unused if 'coord_sys' is NOVAS_ICRS_EQUATOR) sys Dynamical equatorial system type accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) (unused if 'coord_sys' is not NOVAS_ICRS [3]) rag [h] GCRS right ascension in hours. decg [deg] GCRS declination in degrees. [out] ra [h] Right ascension in hours, referred to specified equator and right ascension origin of date. [out] dec [deg] Declination in degrees, referred to specified equator of date.

Returns: 0 if successful, or -1 with errno set to EINVAL if the output pointers are NULL or the coord_sys is invalid, otherwise <0 if an error from vector2radec(), 10–20 error is 10 + error cio_location(); or else 20 + error from cio_basis()

References DEG2RAD, gcrs_to_cirs(), gcrs_to_mod(), gcrs_to_tod(), NOVAS_DYNAMICAL_CIRS, NOVAS_DYNAMICAL_MOD, NOVAS_DYNAMICAL_TOD, and vector2radec().

◆ gcrs_to_cirs() int gcrs_to_cirs ( double jd_tdb, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from the Geocentric Celestial Reference System (GCRS) to the Celestial Intermediate Reference System (CIRS) frame at the given epoch

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in GCRS Input (x, y, z) position or velocity vector [out] out Output position or velocity 3-vector in the True equinox of Date coordinate frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL or the accuracy is invalid, or an error from cio_location(), or else 10 + the error from cio_basis().

See also: gcrs_to_j2000(); cirs_to_gcrs()

Since: 1.0

Author: Attila Kovacs

References cio_basis(), and cio_location().

◆ gcrs_to_j2000() int gcrs_to_j2000 ( const double * in, double * out ) ◆ gcrs_to_mod() int gcrs_to_mod ( double jd_tdb, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from the Geocentric Celestial Reference System (GCRS) to the Mean of Date (MOD) reference frame at the given epoch

Parameters: jd_tdb [day] Barycentric Dynamical Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result in GCRS Input (x, y, z) position or velocity vector [out] out Output position or velocity 3-vector in the Mean wquinox of Date coordinate frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL.

See also: mod_to_gcrs(); gcrs_to_tod()

Since: 1.2

Author: Attila Kovacs

References frame_tie(), ICRS_TO_J2000, NOVAS_JD_J2000, and precession().

◆ gcrs_to_tod() int gcrs_to_tod ( double jd_tdb, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from the Geocentric Celestial Reference System (GCRS) to the True of Date (TOD) reference frame at the given epoch

Parameters: jd_tdb [day] Barycentric Dynamical Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in GCRS Input (x, y, z) position or velocity vector [out] out Output position or velocity 3-vector in the True equinox of Date coordinate frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL.

See also: gcrs_to_cirs(); tod_to_gcrs(); j2000_to_tod()

Since: 1.2

Author: Attila Kovacs

References frame_tie(), ICRS_TO_J2000, and j2000_to_tod().

◆ geo_posvel() short geo_posvel ( double jd_tt, double ut1_to_tt, enum novas_accuracy accuracy, const observer *restrict obs, double *restrict pos, double *restrict vel )

Computes the geocentric GCRS position and velocity of an observer.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. ut1_to_tt [s] TT - UT1 time difference in seconds accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) obs Observer location [out] pos [AU] Position 3-vector of observer, with respect to origin at geocenter, referred to GCRS axes, components in AU. (It may be NULL if not required.) [out] vel [AU/day] Velocity 3-vector of observer, with respect to origin at geocenter, referred to GCRS axes, components in AU/day. (It must be distinct from the pos output vector, and may be NULL if not required)

Returns: 0 if successful, -1 if the 'obs' is NULL or the two output vectors are the same, or else 1 if 'accuracy' is invalid, or 2 if 'obserrver->where' is invalid.

See also: place(); make_observer(); get_ut1_to_tt(); cel_pole()

References ephemeris(), EROT_ERA, geo_posvel(), NOVAS_AIRBORNE_OBSERVER, NOVAS_BARYCENTER, NOVAS_EARTH_INIT, NOVAS_FULL_ACCURACY, NOVAS_OBSERVER_AT_GEOCENTER, NOVAS_OBSERVER_IN_EARTH_ORBIT, NOVAS_OBSERVER_ON_EARTH, NOVAS_REDUCED_ACCURACY, NOVAS_SOLAR_SYSTEM_OBSERVER, NOVAS_TRUE_EQUINOX, sidereal_time(), terra(), tod_to_gcrs(), tt2tdb(), and observer::where.

◆ get_nutation_lp_provider()

Returns the function configured for low-precision IAU 2000 nutation calculations instead of the default nu2000k().

Returns: the function to use for low-precision IAU 2000 nutation calculations

See also: set_nutation_lp_provider(); nutation_angles()

Since: 1.3

Author: Attila Kovacs

◆ get_ut1_to_tt() double get_ut1_to_tt ( int leap_seconds, double dut1 )

Returns the TT - UT1 time difference given the leap seconds and the actual UT1 - UTC time difference as measured and published by IERS.

NOTES:

The current UT1 - UTC time difference, and polar offsets, historical data and near-term projections are published in the <a href="https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html>IERS Bulletins

Parameters: leap_seconds [s] Leap seconds at the time of observations dut1 [s] UT1 - UTC time difference [-0.5:0.5]

Returns: [s] The TT - UT1 time difference that is suitable for used with all calls in this library that require a ut1_to_tt argument.

See also: get_utc_to_tt(); place(); cel_pole()

Since: 1.0

Author: Attila Kovacs

References get_utc_to_tt().

◆ get_utc_to_tt() double get_utc_to_tt ( int leap_seconds )

Returns the difference between Terrestrial Time (TT) and Universal Coordinated Time (UTC)

Parameters: leap_seconds [s] The current leap seconds (see IERS Bulletins)

Returns: [s] The TT - UTC time difference

See also: get_ut1_to_tt(); julian_date()

Since: 1.0

Author: Attila Kovacs

References NOVAS_TAI_TO_TT.

◆ grav_def()

Computes the total gravitational deflection of light for the observed object due to the major gravitating bodies in the solar system. This function valid for an observed body within the solar system as well as for a star.

If 'accuracy' is NOVAS_FULL_ACCURACY (0), the deflections due to the Sun, Jupiter, Saturn, and Earth are calculated. Otherwise, only the deflection due to the Sun is calculated. In either case, deflection for a given body is ignored if the observer is within ~1500 km of the center of the gravitating body.

NOTES:

This function is called by place() to calculate gravitational deflections as appropriate for positioning sources precisely. The gravitational deflection due to planets requires a planet calculator function to be configured, e.g. via set_planet_provider().

REFERENCES:

Klioner, S. (2003), Astronomical Journal 125, 1580-1597, Section 6.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date unused The type of observer frame (no longer used) accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1). In full accuracy mode, it will calculate the deflection due to the Sun, Jupiter, Saturn and Earth. In reduced accuracy mode, only the deflection due to the Sun is calculated. pos_src [AU] Position 3-vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, components in AU. pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. [out] out [AU] Position vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, corrected for gravitational deflection, components in AU. It can be the same vector as the input, but not the same as pos_obs.

Returns: 0 if successful, -1 if any of the pointer arguments is NULL or if the output vector is the same as pos_obs, or the error from obs_planets().

See also: grav_undef(); place(); novas_geom_to_app(); set_planet_provider(); set_planet_provider_hp(); grav_bodies_full_accuracy; grav_bodies_reduced_accuracy

References grav_bodies_full_accuracy, grav_bodies_reduced_accuracy, grav_planets(), NOVAS_FULL_ACCURACY, and obs_planets().

◆ grav_planets() int grav_planets ( const double * pos_src, const double * pos_obs, const novas_planet_bundle *restrict planets, double * out )

Computes the total gravitational deflection of light for the observed object due to the specified gravitating bodies in the solar system. This function is valid for an observed body within the solar system as well as for a star.

NOTES:

The gravitational deflection due to planets requires a planet calculator function to be configured, e.g. via set_planet_provider().

REFERENCES:

Klioner, S. (2003), Astronomical Journal 125, 1580-1597, Section 6.

Parameters: pos_src [AU] Position 3-vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, components in AU. pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. planets Apparent planet data containing positions and velocities for the major gravitating bodies in the solar-system. [out] out [AU] Position vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, corrected for gravitational deflection, components in AU. It can be the same vector as the input, but not the same as pos_obs.

Returns: 0 if successful, -1 if any of the pointer arguments is NULL or if the output vector is the same as pos_obs.

See also: obs_planets(); grav_undo_planets(); grav_def(); novas_geom_to_app(); grav_bodies_full_accuracy; grav_bodies_reduced_accuracy

Since: 1.1

Author: Attila Kovacs

References d_light(), grav_vec(), NOVAS_PLANETS, NOVAS_RMASS_INIT, and novas_vlen().

◆ grav_redshift() double grav_redshift ( double M_kg, double r_m )

Returns the gravitational redshift (z) for light emitted near a massive spherical body at some distance from its center, and observed at some very large (infinite) distance away.

Parameters: M_kg [kg] Mass of gravitating body that is contained inside the emitting radius. r_m [m] Radius at which light is emitted.

Returns: The gravitational redshift (z) for an observer at very large (infinite) distance from the gravitating body.

See also: redshift_vrad(); unredshift_vrad(); novas_z_add()

Since: 1.2

Author: Attila Kovacs

◆ grav_undef() int grav_undef ( double jd_tdb, enum novas_accuracy accuracy, const double * pos_app, const double * pos_obs, double * out )

Computes the gravitationally undeflected position of an observed source position due to the major gravitating bodies in the solar system. This function valid for an observed body within the solar system as well as for a star.

If 'accuracy' is set to zero (full accuracy), three bodies (Sun, Jupiter, and Saturn) are used in the calculation. If the reduced-accuracy option is set, only the Sun is used in the calculation. In both cases, if the observer is not at the geocenter, the deflection due to the Earth is included.

The number of bodies used at full and reduced accuracy can be set by making a change to the code in this function as indicated in the comments.

REFERENCES:

Klioner, S. (2003), Astronomical Journal 125, 1580-1597, Section 6.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) pos_app [AU] Apparent position 3-vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, components in AU. pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. [out] out [AU] Nominal position vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, without gravitational deflection, components in AU. It can be the same vector as the input, but not the same as pos_obs.

Returns: 0 if successful, -1 if any of the pointer arguments is NULL (errno = EINVAL) or if the result did not converge (errno = ECANCELED), or else an error from obs_planets().

See also: grav_def(); novas_app_to_geom(); set_planet_provider(); set_planet_provider_hp(); grav_bodies_full_accuracy; grav_bodies_reduced_accuracy

Since: 1.1

Author: Attila Kovacs

References grav_bodies_full_accuracy, grav_bodies_reduced_accuracy, grav_undo_planets(), NOVAS_FULL_ACCURACY, and obs_planets().

◆ grav_undo_planets() int grav_undo_planets ( const double * pos_app, const double * pos_obs, const novas_planet_bundle *restrict planets, double * out )

Computes the gravitationally undeflected position of an observed source position due to the specified Solar-system bodies.

REFERENCES:

Klioner, S. (2003), Astronomical Journal 125, 1580-1597, Section 6.

Parameters: pos_app [AU] Apparent position 3-vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, components in AU. pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. planets Apparent planet data containing positions and velocities for the major gravitating bodies in the solar-system. [out] out [AU] Nominal position vector of observed object, with respect to origin at observer (or the geocenter), referred to ICRS axes, without gravitational deflection, components in AU. It can be the same vector as the input, but not the same as pos_obs.

Returns: 0 if successful, -1 if any of the pointer arguments is NULL.

See also: obs_planets(); grav_planets(); novas_app_to_geom()

Since: 1.1

Author: Attila Kovacs

References grav_planets(), novas_inv_max_iter, and novas_vlen().

◆ grav_vec() int grav_vec ( const double * pos_src, const double * pos_obs, const double * pos_body, double rmass, double * out )

Corrects position vector for the deflection of light in the gravitational field of an arbitrary body. This function valid for an observed body within the solar system as well as for a star.

NOTES:

This function is called by grav_def() to calculate appropriate gravitational deflections for sources.

REFERENCES:

Murray, C.A. (1981) Mon. Notices Royal Ast. Society 195, 639-648.
See also formulae in Section B of the Astronomical Almanac, or
Kaplan, G. et al. (1989) Astronomical Journal 97, 1197-1210, section iii f.

Parameters: pos_src [AU] Position 3-vector of observed object, with respect to origin at observer (or the geocenter), components in AU. pos_obs [AU] Position vector of gravitating body, with respect to origin at solar system barycenter, components in AU. pos_body [AU] Position 3-vector of gravitating body, with respect to origin at solar system barycenter, components in AU. rmass [1/Msun] Reciprocal mass of gravitating body in solar mass units, that is, Sun mass / body mass. [out] out [AU] Position 3-vector of observed object, with respect to origin at observer (or the geocenter), corrected for gravitational deflection, components in AU. It can the same vector as the input.

Returns: 0 if successful, or -1 if any of the input vectors is NULL.

See also: place(); grav_def()

References novas_vlen().

◆ hor_to_itrs() int hor_to_itrs ( const on_surface *restrict location, double az, double za, double *restrict itrs )

Converts astrometric (unrefracted) azimuth and zenith angles at the specified observer location to a unit position vector in the Earth-fixed ITRS frame.

Parameters: location Observer location on Earth az [deg] astrometric azimuth angle at observer location [0:360]. It may be NULL if not required. za [deg] astrometric zenith angle at observer location [0:180]. It may be NULL if not required. [out] itrs Unit 3-vector direction in Earth-fixed ITRS frame

Returns: 0 if successful, or else -1 if the location or the input vector is NULL.

See also: itrs_to_hor(); itrs_to_cirs(); itrs_to_tod(); refract()

Since: 1.0

Author: Attila Kovacs

◆ ira_equinox()

Compute the intermediate right ascension of the equinox at the input Julian date, using an analytical expression for the accumulated precession in right ascension. For the true equinox, the result is the equation of the origins.

NOTES:

Fixes bug in NOVAS C 3.1, which returned the value for the wrong 'equinox' if 'equinox = 1' was requested for the same 'jd_tbd' and 'accuracy' as a the preceding call with 'equinox = 0'. As a result, the caller ended up with the mean instead of the expected true equinox R.A. value.

REFERENCES:

Capitaine, N. et al. (2003), Astronomy and Astrophysics 412, 567-586, eq. (42).

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date equinox NOVAS_MEAN_EQUINOX (0) or NOVAS_TRUE_EQUINOX (1, or non-zero) accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1, or non-zero)

Returns: [h] Intermediate right ascension of the equinox, in hours (+ or -). If 'equinox' = 1 (i.e true equinox), then the returned value is the equation of the origins.

See also: cio_location(); gcrs_to_cirs()

Deprecated:: (for internal use) There is no good reason why this function should be exposed to users. It is intended only for cio_location() internally.

References e_tilt(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUINOX.

◆ itrs_to_cirs() int itrs_to_cirs ( double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double * in, double * out )

Rotates a position vector from the Earth-fixed ITRS frame to the dynamical CIRS frame of date (IAU 2000 standard method).

If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Kaplan, G. H. (2003), 'Another Look at Non-Rotating Origins', Proceedings of IAU XXV Joint Discussion 16.

Parameters: jd_tt_high [day] High-order part of Terrestrial Time (TT) based Julian date. jd_tt_low [day] Low-order part of Terrestrial Time (TT) based Julian date. ut1_to_tt [s] TT - UT1 Time difference in seconds accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) xp [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. in Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system) [out] out Position vector, geocentric equatorial rectangular coordinates, referred to CIRS axes (celestial system).

Returns: 0 if successful, -1 if either of the vector arguments is NULL, 1 if 'accuracy' is invalid, or else 10 + the error from cio_location(), or 20 + error from cio_basis().

See also: itrs_to_tod(); cirs_to_itrs(); cirs_to_gcrs()

Since: 1.0

Author: Attila Kovacs

References EROT_ERA, NOVAS_DYNAMICAL_CLASS, and ter2cel().

◆ itrs_to_hor() int itrs_to_hor ( const on_surface *restrict location, const double *restrict itrs, double *restrict az, double *restrict za )

Converts a position vector in the Earth-fixed ITRS frame to astrometric (unrefracted) azimuth and zenith angles at the specified observer location.

Parameters: location Observer location on Earth itrs 3-vector position in Earth-fixed ITRS frame [out] az [deg] astrometric azimuth angle at observer location [0:360]. It may be NULL if not required. [out] za [deg] astrometric zenith angle at observer location [0:180]. It may be NULL if not required.

Returns: 0 if successful, or else -1 if the location or the input vector is NULL.

See also: hor_to_itrs(); cirs_to_itrs(); tod_to_itrs(); refract_astro()

Since: 1.0

Author: Attila Kovacs

◆ itrs_to_tod() int itrs_to_tod ( double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double * in, double * out )

Rotates a position vector from the Earth-fixed ITRS frame to the dynamical True of Date (TOD) frame of date (pre IAU 2000 method).

If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Kaplan, G. H. (2003), 'Another Look at Non-Rotating Origins', Proceedings of IAU XXV Joint Discussion 16.

Parameters: jd_tt_high [day] High-order part of Terrestrial Time (TT) based Julian date. jd_tt_low [day] Low-order part of Terrestrial Time (TT) based Julian date. ut1_to_tt [s] TT - UT1 Time difference in seconds accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) xp [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. in Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system) [out] out Position vector, geocentric equatorial rectangular coordinates, referred to True of Date (TOD) axes (celestial system)

Returns: 0 if successful, -1 if either of the vector arguments is NULL, 1 if 'accuracy' is invalid, or else 10 + the error from cio_location(), or 20 + error from cio_basis().

See also: itrs_to_cirs(); tod_to_itrs(); tod_to_j2000()

Since: 1.0

Author: Attila Kovacs

References EROT_GST, NOVAS_DYNAMICAL_CLASS, and ter2cel().

◆ j2000_to_gcrs() int j2000_to_gcrs ( const double * in, double * out ) ◆ j2000_to_tod() int j2000_to_tod ( double jd_tdb, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from J2000 coordinates to the True of Date (TOD) reference frame at the given epoch

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in Input (x, y, z) position or velocity vector in rectangular equatorial coordinates at J2000 [out] out Output position or velocity 3-vector in the True equinox of Date coordinate frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL or the accuracy is invalid.

See also: j2000_to_gcrs(); tod_to_j2000(); gcrs_to_j2000()

Since: 1.0

Author: Attila Kovacs

References NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NUTATE_MEAN_TO_TRUE, nutation(), and precession().

◆ julian_date() double julian_date ( short year, short month, short day, double hour )

Returns the Julian day for a given astronomical calendar date. Input time value can be based on any UT-like time scale (UTC, UT1, TT, etc.) - output Julian day will have the same basis.

NOTES:

The Gregorian calendar was introduced on 1582 October 15 only. Prior to that, astronomical dates are Julian/Roman dates, so the day before the reform was 1582 October 4. You can also use novas_jd_from_date() to convert dates with more flexibility.
B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.
Added argument range checking in v1.3.0, returning NAN if the month or day are out of the normal range (for a leap year).

REFERENCES:

Fliegel, H. & Van Flandern, T. Comm. of the ACM, Vol. 11, No. 10, October 1968, p. 657.

Parameters: year [yr] Astronomical calendar year. B.C. years can be simply represented as <=0, e.g. 1 B.C. as 0, and X B.C. as (1 - X). month [month] Astronomical calendar month [1:12] day [day] Astronomical day of month [1:31] hour [hr] Hour of day [0:24]

Returns: [day] the fractional Julian date for the input calendar date, ot NAN if month or day components are out of range.

See also: novas_jd_from_date(); novas_jd_to_date(); get_utc_to_tt(); get_ut1_to_tt(); tt2tdb()

References NOVAS_ASTRONOMICAL_CALENDAR, and novas_jd_from_date().

◆ light_time() short light_time ( double jd_tdb, const object *restrict body, const double * pos_obs, double tlight0, enum novas_accuracy accuracy, double * pos_src_obs, double *restrict tlight )

Computes the geocentric position of a solar system body, as antedated for light-time.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date body Pointer to structure containing the designation for the solar system body pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. tlight0 [day] First approximation to light-time, in days (can be set to 0.0 if unknown). accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos_src_obs [AU] Position 3-vector of body, with respect to origin at observer (or the geocenter), referred to ICRS axes, components in AU. It can be the same vector as either of the inputs. [out] tlight [day] Calculated light time

Returns: 0 if successful, -1 if any of the poiinter arguments is NULL, 1 if the algorithm failed to converge after 10 iterations, or 10 + the error from ephemeris().

See also: light_time2(); place()

References light_time2().

◆ light_time2() int light_time2 ( double jd_tdb, const object *restrict body, const double *restrict pos_obs, double tlight0, enum novas_accuracy accuracy, double * p_src_obs, double *restrict v_ssb, double *restrict tlight )

Computes the geocentric position and velocity of a solar system body, as antedated for light-time. It is effectively the same as the original NOVAS C light_time(), except that this returns the antedated source velocity vector also.

NOTES:

This function is called by place() to calculate observed positions, radial velocity, and distance for the time when the observed light originated from the source.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date body Pointer to structure containing the designation for the solar system body pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. tlight0 [day] First approximation to light-time, in days (can be set to 0.0 if unknown). accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] p_src_obs [AU] Position 3-vector of body, relative to observer, referred to ICRS axes, components in AU. [out] v_ssb [AU/day] Velocity 3-vector of body, with respect to the Solar-system barycenter, referred to ICRS axes, components in AU/day. [out] tlight [day] Calculated light time, or NAN when returning with an error code.

Returns: 0 if successful, -1 if any of the pointer arguments is NULL or if the output vectors are the same or if they are the same as pos_obs, 1 if the algorithm failed to converge after 10 iterations, or 10 + the error from ephemeris().

See also: light_time(); place()

Since: 1.0

Author: Attila Kovacs

References bary2obs(), ephemeris(), NOVAS_BARYCENTER, NOVAS_FULL_ACCURACY, and novas_inv_max_iter.

◆ limb_angle() int limb_angle ( const double * pos_src, const double * pos_obs, double *restrict limb_ang, double *restrict nadir_ang )

Determines the angle of an object above or below the Earth's limb (horizon). The geometric limb is computed, assuming the Earth to be an airless sphere (no refraction or oblateness is included). The observer can be on or above the Earth. For an observer on the surface of the Earth, this function returns the approximate unrefracted elevation.

Parameters: pos_src [AU] Position 3-vector of observed object, with respect to origin at geocenter, components in AU. pos_obs [AU] Position 3-vector of observer, with respect to origin at geocenter, components in AU. [out] limb_ang [deg] Angle of observed object above (+) or below (-) limb in degrees, or NAN if reurning with an error. It may be NULL if not required. [out] nadir_ang Nadir angle of observed object as a fraction of apparent radius of limb: lt;1.0 if below the limb; 1.0 on the limb; or >1.0 if above the limb. Returns NAN in case of an error return. It may be NULL if not required.

Returns: 0 if successful, or -1 if either of the input vectors is NULL or if either input position is a null vector (at the geocenter).

See also: place()

References M_PI, and novas_vlen().

◆ local_planet() short local_planet ( double jd_tt, const object *restrict ss_body, double ut1_to_tt, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis )

Computes the local apparent place of a solar system body, in the GCRS. This is the same as calling place() for the body for the same observer location and NOVAS_GCRS as the reference system, except the different set of return values used.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. ss_body Pointer to structure containing the body designation for the solar system body. ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. position Position of the observer accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Local right ascension in hours, referred to the GCRS (it may be NULL if not required). [out] dec [deg] Local right ascension in hours, referred to the GCRS (it may be NULL if not required). [out] dis [AU] True distance from Earth to the body at 'jd_tt' in AU (it may be NULL if not required).

Returns: 0 if successful, or -1 if the object argument is NULL, or else 1 if the value of 'where' in structure 'location' is invalid, or 10 + the error code from place().

See also: astro_planet(); topo_planet(); virtual_planet(); app_star(); get_ut1_to_tt()

References make_observer(), NOVAS_GCRS, NOVAS_OBSERVER_ON_EARTH, and radec_planet().

◆ local_star() short local_star ( double jd_tt, double ut1_to_tt, const cat_entry *restrict star, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec )

Computes the local apparent place of a star at date 'jd_tt', in the GCRS, given its catalog mean place, proper motion, parallax, and radial velocity.

Notwithstanding the different set of return values, this is the same as calling place_star() with the same observer location NOVAS_GCRS for an object that specifies the star.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992), Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. position Position of the observer accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Local right ascension in hours, referred to the GCRS (it may be NULL if not required). [out] dec [deg] Local right ascension in hours, referred to the GCRS (it may be NULL if not required).

Returns: 0 if successful, or -1 if any of the required pointer arguments is NULL, or else 20 + the error from place().

See also: place_star(); app_star(); astro_star(); topo_star(); virtual_star(); astro_planet(); get_ut1_to_tt()

References make_observer(), NOVAS_GCRS, NOVAS_OBSERVER_ON_EARTH, and radec_star().

◆ make_airborne_observer() int make_airborne_observer ( const on_surface * location, const double * vel, observer * obs )

Populates an 'observer' data structure for an observer moving relative to the surface of Earth, such as an airborne observer. Airborne observers have an earth fixed momentary location, defined by longitude, latitude, and altitude, the same was as for a stationary observer on Earth, but are moving relative to the surface, such as in an aircraft or balloon observatory.

Parameters: location Current longitude, latitude and altitude, and local weather (temperature and pressure) vel [km/s] Surface velocity. [out] obs Pointer to data structure to populate.

Returns: 0 if successful, or -1 if the output argument is NULL.

See also: make_observer_at geocenter(); make_observer_in_space(); make_observer_on_surface(); make_solar_system_observer(); novas_calc_geometric_position(); place()

Since: 1.1

Author: Attila Kovacs

References IN_SPACE_INIT, make_observer(), NOVAS_AIRBORNE_OBSERVER, and in_space::sc_vel.

◆ make_cat_entry() short make_cat_entry ( const char *restrict star_name, const char *restrict catalog, long cat_num, double ra, double dec, double pm_ra, double pm_dec, double parallax, double rad_vel, cat_entry * star )

Populates the data structure for a 'catalog' source, such as a star.

Parameters: star_name Object name (less than SIZE_OF_OBJ_NAME in length). It may be NULL if not relevant. catalog Catalog identifier (less than SIZE_OF_CAT_NAME in length). E.g. 'HIP' = Hipparcos, 'TY2' = Tycho-2. It may be NULL if not relevant. cat_num Object number in the catalog. ra [h] Right ascension of the object (hours). dec [deg] Declination of the object (degrees). pm_ra [mas/yr] Proper motion in right ascension (milliarcseconds/year). pm_dec [mas/yr] Proper motion in declination (milliarcseconds/year). parallax [mas] Parallax (milliarcseconds). rad_vel [km/s] Radial velocity relative to the Solar-System Barycenter (SSB) To convert velocities defined against the Local Standard of Rest (LSR), you may use novas_lsr_to_ssb_vel() to convert appropriately. [out] star Pointer to data structure to populate.

Returns: 0 if successful, or -1 if the output argument is NULL, 1 if the 'star_name' is too long or 2 if the 'catalog' name is too long.

See also: novas_lsr_to_ssb_vel(); make_redshifted_cat_entry(); make_cat_object_sys(); transform_cat()

References cat_entry::catalog, cat_entry::dec, cat_entry::parallax, cat_entry::promodec, cat_entry::promora, cat_entry::ra, rad_vel(), cat_entry::radialvelocity, SIZE_OF_CAT_NAME, SIZE_OF_OBJ_NAME, cat_entry::starname, and cat_entry::starnumber.

◆ make_cat_object() ◆ make_cat_object_sys() int make_cat_object_sys ( const cat_entry * star, const char *restrict system, object * source )

Populates and object data structure with the data for a catalog source for a given system of catalog coordinates.

Parameters: star Pointer to structure to populate with the catalog data for a celestial object located outside the solar system. system Input catalog coordinate system epoch, e.g. "ICRS", "B1950.0", "J2000.0", "FK4", "FK5", or "HIP". In general, any Besselian or Julian year epoch can be used by year (e.g. "B1933.193" or "J2022.033"), or else the fixed value listed. If 'B' or 'J' is ommitted in front of the epoch year, then Besselian epochs are assumed prior to 1984.0. [out] source Pointer to the celestial object data structure to be populated with the corresponding ICRS catalog coordinates, after appying proper-motion and precession corrections as appropriate.

Returns: 0 if successful, or -1 if any argument is NULL or if the input 'system' is invalid, or else 5 if 'name' is too long.

See also: make_cat_object(); make_redshifted_object_sys(); novas_jd_for_epoch(); make_cat_entry(); place(); NOVAS_SYSTEM_ICRS; NOVAS_SYSTEM_HIP; NOVAS_SYSTEM_J2000; NOVAS_SYSTEM_B1950

Since: 1.3

Author: Attila Kovacs

References make_cat_object(), and object::star.

◆ make_ephem_object() int make_ephem_object ( const char * name, long num, object * body )

Sets a celestial object to be a Solar-system ephemeris body. Typically this would be used to define minor planets, asteroids, comets and planetary satellites.

Parameters: name Name of object. By default converted to upper-case, unless novas_case_sensitive() was called with a non-zero argument. Max. SIZE_OF_OBJ_NAME long, including termination. If the ephemeris provider uses names, then the name should match those of the ephemeris provider – otherwise it is not important. num Solar-system body ID number (e.g. NAIF). The number should match the needs of the ephemeris provider used with NOVAS. (If the ephemeris provider is by name and not ID number, then the number here is not important). [out] body Pointer to structure to populate.

Returns: 0 if successful, or else -1 if the 'body' pointer is NULL or the name is too long.

See also: set_ephem_provider(); make_planet(); make_cat_entry(); novas_geom_posvel(); place()

Since: 1.0

Author: Attila Kovacs

References make_object(), and NOVAS_EPHEM_OBJECT.

◆ make_in_space() int make_in_space ( const double * sc_pos, const double * sc_vel, in_space * loc )

Populates an 'in_space' data structure, for an observer situated on a near-Earth spacecraft, with the provided position and velocity components. Both input vectors are assumed with respect to true equator and equinox of date.

Parameters: sc_pos [km] Geocentric (x, y, z) position vector in km. NULL defaults to the origin sc_vel [km/s] Geocentric (x, y, z) velocity vector in km/s. NULL defaults to zero speed. [out] loc Pointer to earth-orbit location data structure to populate.

Returns: 0 if successful, or -1 if the output argument is NULL.

See also: make_observer_in_space(); make_on_surface(); IN_SPACE_INIT

References in_space::sc_pos, and in_space::sc_vel.

◆ make_object()

Populates an object data structure using the parameters provided. By default (for compatibility with NOVAS C) source names are converted to upper-case internally. You can however enable case-sensitive processing by calling novas_case_sensitive() before.

NOTES:

This call does not initialize the orbit field (added in v1.2) with zeroes to remain ABI compatible with versions <1.2, and to avoid the possiblity of segfaulting if used to initialize a legacy object variable.

Parameters: type The type of object. NOVAS_PLANET (0), NOVAS_EPHEM_OBJECT (1) or NOVAS_CATALOG_OBJECT (2), or NOVAS_ORBITAL_OBJECT (3). number The novas ID number (for solar-system bodies only, otherwise ignored) name The name of the object (case insensitive). It should be shorter than SIZE_OF_OBJ_NAME or else an error will be returned. The name is converted to upper internally unless novas_case_sensitive() was called before to change that. star Pointer to structure to populate with the catalog data for a celestial object located outside the solar system. Used only if type is NOVAS_CATALOG_OBJECT, otherwise ignored and can be NULL. [out] source Pointer to the celestial object data structure to be populated.

Returns: 0 if successful, or -1 if 'cel_obj' is NULL or when type is NOVAS_CATALOG_OBJECT and 'star' is NULL, or else 1 if 'type' is invalid, 2 if 'number' is out of legal range or 5 if 'name' is too long.

See also: novas_case_sensitive(); make_cat_object(); make_redshifted_object(); make_planet(); make_ephem_object(); make_orbital_object(); novas_geom_posvel(); place()

References object::name, NOVAS_CATALOG_OBJECT, NOVAS_OBJECT_TYPES, NOVAS_ORBITAL_OBJECT, NOVAS_PLANET, NOVAS_PLANETS, object::number, object::star, and object::type.

◆ make_observer()

Populates an 'observer' data structure given the parameters. The output data structure may be used an the the inputs to NOVAS-C function 'place()'.

Parameters: where The location type of the observer loc_surface Pointer to data structure that defines a location on Earth's surface. Used only if 'where' is NOVAS_OBSERVER_ON_EARTH, otherwise can be NULL. loc_space Pointer to data structure that defines a near-Earth location in space. Used only if 'where' is NOVAS_OBSERVER_IN_EARTH_ORBIT, otherwise can be NULL. [out] obs Pointer to observer data structure to populate.

Returns: 0 if successful, -1 if a required argument is NULL, or 1 if the 'where' argument is invalid.

See also: make_observer_at_geocenter(); make_observer_on_surface(); make_observer_in_space(); make_solar_system_observer()

References observer::near_earth, NOVAS_AIRBORNE_OBSERVER, NOVAS_OBSERVER_AT_GEOCENTER, NOVAS_OBSERVER_IN_EARTH_ORBIT, NOVAS_OBSERVER_ON_EARTH, NOVAS_SOLAR_SYSTEM_OBSERVER, observer::on_surf, in_space::sc_vel, and observer::where.

◆ make_observer_at_geocenter() int make_observer_at_geocenter ( observer *restrict obs ) ◆ make_observer_in_space() int make_observer_in_space ( const double * sc_pos, const double * sc_vel, observer * obs )

Populates an 'observer' data structure, for an observer situated on a near-Earth spacecraft, with the specified geocentric position and velocity vectors. Both input vectors are with respect to true equator and equinox of date. The output data structure may be used an the the inputs to NOVAS-C function 'place()'.

Parameters: sc_pos [km] Geocentric (x, y, z) position vector in km. sc_vel [km/s] Geocentric (x, y, z) velocity vector in km/s. [out] obs Pointer to the data structure to populate

Returns: 0 if successful, or -1 if the output argument is NULL.

See also: make_observer_on_surface(); make_observer_at_geocenter(); place()

References make_in_space(), make_observer(), and NOVAS_OBSERVER_IN_EARTH_ORBIT.

◆ make_observer_on_surface() int make_observer_on_surface ( double latitude, double longitude, double height, double temperature, double pressure, observer *restrict obs )

Populates and 'on_surface' data structure with the specified location defining parameters of the observer. The output data structure may be used an the the inputs to NOVAS-C function 'place()'.

Parameters: latitude [deg] Geodetic (ITRS) latitude in degrees; north positive. longitude [deg] Geodetic (ITRS) longitude in degrees; east positive. height [m] Altitude over se level of the observer (meters). temperature [C] Temperature (degrees Celsius). pressure [mbar] Atmospheric pressure (millibars). [out] obs Pointer to the data structure to populate.

Returns: 0 if successful, or -1 if the output argument is NULL.

See also: make_observer_in_space(); make_observer_at_geocenter(); place()

References make_observer(), make_on_surface(), and NOVAS_OBSERVER_ON_EARTH.

◆ make_on_surface() int make_on_surface ( double latitude, double longitude, double height, double temperature, double pressure, on_surface *restrict loc )

Populates an 'on_surface' data structure, for an observer on the surface of the Earth, with the given parameters.

Note, that because this is an original NOVAS C routine, it does not have an argument to set a humidity value (e.g. for radio refraction). As such, the humidity value remains undefined after this call. To set the humidity, set the output structure's field after calling this funcion. Its unit is [%], and so the range is 0.0–100.0.

NOTES

This implementation breaks strict v1.0 ABI compatibility since it writes to (initializes) a field (humidity) that was not yet part of the on_surface structure in v1.0. As such, linking SuperNOVAS v1.1 or later with application code compiled for SuperNOVAS v1.0 can result in memory corruption or segmentation fault when this function is called. To be safe, make sure your application has been (re)compiled against SuperNOVAS v1.1 or later.

Parameters: latitude [deg] Geodetic (ITRS) latitude in degrees; north positive. longitude [deg] Geodetic (ITRS) longitude in degrees; east positive. height [m] Altitude over sea level of the observer (meters). temperature [C] Temperature (degrees Celsius) [-120:70]. pressure [mbar] Atmospheric pressure (millibars) [0:1200]. [out] loc Pointer to Earth location data structure to populate.

Returns: 0 if successful, or -1 if the output argument is NULL, or if the temperature or pressure values are impossible for an Earth based observer.

See also: make_observer_on_surface(); make_in_space(); ON_SURFACE_INIT; ON_SURFACE_LOC

◆ make_planet() ◆ make_redshifted_cat_entry() int make_redshifted_cat_entry ( const char * name, double ra, double dec, double z, cat_entry * source )

Populates a celestial object data structure with the parameters for a redhifted catalog source, such as a distant quasar or galaxy. It is similar to make_cat_object() except that it takes a Doppler-shift (z) instead of radial velocity and it assumes no parallax and no proper motion (appropriately for a distant redshifted source). The catalog name is set to EXT to indicate an extragalactic source, and the catalog number defaults to 0. The user may change these default field values as appropriate afterwards, if necessary.

Parameters: name Object name (less than SIZE_OF_OBJ_NAME in length). It may be NULL. ra [h] Right ascension of the object (hours). dec [deg] Declination of the object (degrees). z Redhift value (λ_obs / λ_rest - 1 = f_rest / f_obs - 1). [out] source Pointer to structure to populate.

Returns: 0 if successful, or 5 if 'name' is too long, else -1 if the 'source' pointer is NULL.

See also: make_redshifted_object_sys(); novas_v2z()

Since: 1.2

Author: Attila Kovacs

References make_cat_entry(), and novas_z2v().

◆ make_redshifted_object() int make_redshifted_object ( const char * name, double ra, double dec, double z, object * source )

Parameters: name Object name (less than SIZE_OF_OBJ_NAME in length). It may be NULL. ra [h] ICRS Right ascension of the object (hours). dec [deg] ICRS Declination of the object (degrees). z Redhift value (λ_obs / λ_rest - 1 = f_rest / f_obs - 1). [out] source Pointer to structure to populate.

Returns: 0 if successful, or 5 if 'name' is too long, else -1 if the 'source' pointer is NULL.

See also: make_redshifted_object_sys(); make_cat_object(); novas_v2z()

Since: 1.2

Author: Attila Kovacs

References make_cat_object(), and make_redshifted_cat_entry().

◆ make_redshifted_object_sys() int make_redshifted_object_sys ( const char * name, double ra, double dec, const char *restrict system, double z, object * source )

Populates a celestial object data structure with the parameters for a redhifted catalog source, such as a distant quasar or galaxy, for a given system of catalog coordinates.

Parameters: name Object name (less than SIZE_OF_OBJ_NAME in length). It may be NULL. ra [h] ICRS Right ascension of the object (hours). dec [deg] ICRS Declination of the object (degrees). system Input catalog coordinate system epoch, e.g. "ICRS", "B1950.0", "J2000.0", "FK4", "FK5", or "HIP". In general, any Besselian or Julian year epoch can be used by year (e.g. "B1933.193" or "J2022.033"), or else the fixed value listed. If 'B' or 'J' is ommitted in front of the epoch year, then Besselian epochs are assumed prior to 1984.0. z Redhift value (λ_obs / λ_rest - 1 = f_rest / f_obs - 1). [out] source Pointer to the celestial object data structure to be populated with the corresponding ICRS catalog coordinates.

Returns: 0 if successful, or -1 if any of the pointer arguments is NULL or the 'system' is invalid, or else 1 if 'type' is invalid, 2 if 'number' is out of legal range or 5 if 'name' is too long.

See also: make_redshifted_object(); make_cat_object_sys(); novas_jd_for_epoch(); place(); NOVAS_SYSTEM_ICRS; NOVAS_SYSTEM_HIP; NOVAS_SYSTEM_J2000; NOVAS_SYSTEM_B1950

Since: 1.3

Author: Attila Kovacs

References make_redshifted_object(), and object::star.

◆ make_solar_system_observer() int make_solar_system_observer ( const double * sc_pos, const double * sc_vel, observer * obs )

Populates an 'observer' data structure, for an observer situated on a near-Earth spacecraft, with the specified geocentric position and velocity vectors. Solar-system observers are similar to observers in Earth-orbit but their momentary position and velocity is defined relative to the Solar System Barycenter, instead of the geocenter.

Parameters: sc_pos [AU] Solar-system barycentric (x, y, z) position vector in ICRS. sc_vel [AU/day] Solar-system barycentric (x, y, z) velocity vector in ICRS. [out] obs Pointer to the data structure to populate

Returns: 0 if successful, or -1 if the output argument is NULL.

See also: make_observer_in_space(); make_observer_on_surface(); make_observer_at_geocenter(); make_airborne_observer(); novas_calc_geometric_position(); place()

Since: 1.1

Author: Attila Kovacs

References make_in_space(), make_observer(), and NOVAS_SOLAR_SYSTEM_OBSERVER.

◆ mean_obliq() double mean_obliq ( double jd_tdb )

Computes the mean obliquity of the ecliptic.

REFERENCES:

Capitaine et al. (2003), Astronomy and Astrophysics 412, 567-586.

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date

Returns: [arcsec] Mean obliquity of the ecliptic in arcseconds.

See also: e_tilt(); equ2ecl(); ecl2equ(); tt2tdb()

◆ mean_star() short mean_star ( double jd_tt, double tra, double tdec, enum novas_accuracy accuracy, double *restrict ira, double *restrict idec )

Computes the ICRS position of a star, given its True of Date (TOD) apparent place at date 'jd_tt'. Proper motion, parallax and radial velocity are assumed to be zero.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. tra [h] Apparent (TOD) right ascension in hours, referred to true equator and equinox of date. tdec [deg] Apparent (TOD) declination in degrees, referred to true equator and equinox of date. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ira [h] ICRS right ascension in hours, or NAN when returning with an error code. [out] idec [deg] ICRS declination in degrees, or NAN when returning with an error code.

Returns: 0 if successful; -1 if the supplied output pointers are NULL, 1 if the iterative process did not converge after 30 iterations, or an error from vector2radec(), or else > 10 + an error from app_star().

See also: make_cat_entry(); proper_motion(); precession()

References app_star(), CAT_ENTRY_INIT, cat_entry::dec, novas_inv_max_iter, precession(), cat_entry::ra, starvectors(), and vector2radec().

◆ mod_to_gcrs() int mod_to_gcrs ( double jd_tdb, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from Mean of Date (MOD) reference frame at the given epoch to the Geocentric Celestial Reference System(GCRS)

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date that defines the input epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result in Input (x, y, z) position or velocity 3-vector in the Mean equinox of Date coordinate frame. [out] out Output GCRS position or velocity vector. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL.

See also: gcrs_to_mod(); tod_to_gcrs()

Since: 1.2

Author: Attila Kovacs

References frame_tie(), J2000_TO_ICRS, NOVAS_JD_J2000, and precession().

◆ novas_app_to_geom()

Converts an observed apparent sky position of a source to an ICRS geometric position, by undoing the gravitational deflection and aberration corrections.

Parameters: frame The observer frame, defining the location and time of observation sys The reference system in which the observed position is specified. ra [h] Observed ICRS right-ascension of the source dec [deg] Observed ICRS declination of the source dist [AU] Observed distance from observer. A value of <=0 will translate to 10¹⁵ AU (around 5 Gpc). [out] geom_icrs [AU] The corresponding geometric position for the source, in ICRS.

Returns: 0 if successful, or else an error from grav_undef2(), or -1 (errno will indicate the type of error).

See also: novas_geom_to_app(); novas_hor_to_app(); novas_geom_to_hor(); novas_transform_vector()

Since: 1.1

Author: Attila Kovacs

References grav_undo_planets(), NOVAS_CIRS, NOVAS_ITRS, NOVAS_J2000, NOVAS_MOD, NOVAS_REFERENCE_SYSTEMS, NOVAS_TIRS, NOVAS_TOD, radec2vector(), spin(), wobble(), and WOBBLE_ITRS_TO_TIRS.

◆ novas_app_to_hor()

Converts an observed apparent position vector in the specified coordinate system to local horizontal coordinates in the specified observer frame. The observer must be located on the surface of Earth, or else the call will return with an error. The caller may optionally supply a refraction model of choice to calculate an appropriate elevation angle that includes a refraction correction for Earth's atmosphere. If no such model is provided the calculated elevation will be the astrometric elevation without a refraction correction.

Parameters: frame Observer frame, defining the time and place of observation (on Earth). sys Astronomical coordinate system in which the observed position is given. ra [h] Observed apparent right ascension (R.A.) coordinate dec [deg] Observed apparent declination coordinate ref_model An appropriate refraction model, or NULL to calculate unrefracted elevation. Depending on the refraction model, you might want to make sure that the weather parameters were set when the observing frame was defined. [out] az [deg] Calculated azimuth angle. It may be NULL if not required. [out] el [deg] Calculated elevation angle. It may be NULL if not required.

Returns: 0 if successful, or else an error from tod_to_itrs() or cirs_to_itrs(), or -1 (errno will indicate the type of error).

See also: novas_hor_to_app(); novas_app_to_geom(); novas_standard_refraction(); novas_optical_refraction(); novas_radio_refraction(); novas_wave_refraction()

Since: 1.1

Author: Attila Kovacs

References novas_timespec::fjd_tt, novas_timespec::ijd_tt, itrs_to_hor(), NOVAS_AIRBORNE_OBSERVER, NOVAS_CIRS, NOVAS_GCRS, NOVAS_ICRS, NOVAS_ITRS, NOVAS_J2000, NOVAS_MOD, NOVAS_OBSERVER_ON_EARTH, NOVAS_REFRACT_ASTROMETRIC, NOVAS_TIRS, NOVAS_TOD, radec2vector(), spin(), wobble(), WOBBLE_PEF_TO_ITRS, and WOBBLE_TIRS_TO_ITRS.

◆ novas_case_sensitive() void novas_case_sensitive ( int value )

Enables or disables case-sensitive processing of the object name. The effect is not retroactive. The setting will only affect the celestial objects that are defined after the call. Note, that catalog names, set via make_cat_entry() are always case sensitive regardless of this setting.

Parameters: value (boolean) TRUE (non-zero) to enable case-sensitive object names, or else FALSE (0) to convert names to upper case only (NOVAS C compatible behavior).

See also: make_object()

Since: 1.0

Author: Attila Kovacs

◆ novas_change_observer()

Change the observer location for an observing frame.

Parameters: orig Pointer to original observing frame obs New observer location [out] out Observing frame to populate with a original frame data and new observer location. It can be the same as the input.

Returns: 0 if successfule or else an an error code from geo_posvel() (errno will also indicate the type of error).

See also: novas_make_frame()

Since: 1.1

Author: Attila Kovacs

References novas_frame::accuracy, grav_bodies_full_accuracy, grav_bodies_reduced_accuracy, NOVAS_FULL_ACCURACY, novas_get_time(), NOVAS_TDB, obs_planets(), novas_frame::obs_pos, novas_frame::observer, novas_frame::planets, novas_frame::state, and novas_frame::time.

◆ novas_date() double novas_date ( const char *restrict date )

Returns a Julian date (in non-specific timescale) corresponding the specified input string date/time. E.g. for "2025-02-28T09:41:12.041+0200", with some flexibility on how the date is represented as long as it's YMD date followed by HMS time. For other date formats (MDY or DMY) you can use novas_parse_date_format() instead.

Parameters: date The date specification, possibly including time and timezone, in a standard format. See novas_parse_date() on more information on acceptable date/time formats.

Returns: [day] The Julian Day corresponding to the string date/time specification or NAN if the string is NULL or if it does not specify a date/time in the expected format.

Since: 1.3

Author: Attila Kovacs

See also: novas_date_scale(); novas_parse_date(); novas_parse_date_format(); novas_iso_timestamp()

References novas_parse_date().

◆ novas_date_scale() double novas_date_scale ( const char *restrict date, enum novas_timescale *restrict scale )

Returns a Julian date and the timescale corresponding the specified input string date/time and timescale marker. E.g. for "2025-02-28T09:41:12.041+0200 TAI", with some flexibility on how the date is represented as long as it's YMD date followed by HMS time. For other date formats (MDY or DMY) you can use novas_parse_date_format() instead.

Parameters: date The date specification, possibly including time and timezone, in a standard format. See novas_parse_date() on more information on acceptable date/time formats. [out] scale The timescale constant, or else -1 if the string could not be parsed into a date and timescale. If the string is a bare timestamp without an hint of a timescale marker, then NOVAS_UTC will be assumed.

Returns: [day] The Julian Day corresponding to the string date/time specification or NAN if the string is NULL or if it does not specify a date/time in the expected format.

Since: 1.3

Author: Attila Kovacs

See also: novas_date(); novas_timestamp()

References novas_parse_date(), and novas_parse_timescale().

◆ novas_day_of_week() int novas_day_of_week ( double tjd )

Returns the one-based ISO 8601 day-of-week index of a given Julian Date. The ISO 8601 week begins on Monday, thus index 1 corresponds to Monday, while index 7 is a Sunday.

Parameters: tjd [day] Julian Date in the timescale of choice. (e.g. UTC-based if you want a UTC-based return value).

Returns: [1:7] The day-of-week index in the same timescale as the input date. 1:Monday ... 7:Sunday.

Since: 1.4

Author: Attila Kovacs

See also: novas_day_of_year(); novas_jd_to_date()

References NOVAS_JD_J2000.

◆ novas_day_of_year()

Returns the one-based day index in the calendar year for a given Julian Date.

Parameters: tjd [day] Julian Date in the timescale of choice. (e.g. UTC-based if you want a UTC-based return value). calendar The type of calendar to use: NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_GREGORIAN_CALENDAR, or NOVAS_ROMAN_CALENDAR. [out] year [yr] Optional pointer to which to return the calendar year. It may be NULL if not required.

Returns: [1:366] The day-of-year index in the same timescale as the input date.

Since: 1.4

Author: Attila Kovacs

See also: novas_day_of_week(); novas_jd_to_date()

References NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_JD_START_GREGORIAN, novas_jd_to_date(), and NOVAS_ROMAN_CALENDAR.

◆ novas_debug()

==========================================================================

Enables or disables reporting errors and traces to the standard error stream.

Parameters: mode NOVAS_DEBUG_OFF (0; or <0), NOVAS_DEBUG_ON (1), or NOVAS_DEBUG_EXTRA (2; or >2).

Since: 1.0

Author: Attila Kovacs

See also: novas_get_debug_mode()

References NOVAS_DEBUG_EXTRA.

◆ novas_diff_tcb()

Returns the Barycentric Coordinate Time (TCB) based time difference (t1 - t2) in days between two astronomical time specifications. TCB progresses slightly faster than time on Earth, at a rate about 1.6&times10^-8 higher, due to the lack of gravitational time dilation by the Earth or Sun.

Parameters: t1 First time t2 Second time

Returns: [s] Precise TCB time difference (t1-t2), or NAN if one of the inputs was NULL (errno will be set to EINVAL)

See also: novas_diff_tcg(); novas_diff_time()

Since: 1.1

Author: Attila Kovacs

References novas_diff_time().

◆ novas_diff_tcg()

Returns the Geocentric Coordinate Time (TCG) based time difference (t1 - t2) in days between two astronomical time specifications. TCG progresses slightly faster than time on Earth, at a rate about 7&times10^-10 higher, due to the lack of gravitational time dilation by Earth. TCG is an appropriate time measure for a spacecraft that is in the proximity of the orbit of Earth, but far enough from Earth such that the relativistic effects of Earth's gravity can be ignored.

Parameters: t1 First time t2 Second time

Returns: [s] Precise TCG time difference (t1-t2), or NAN if one of the inputs was NULL (errno will be set to EINVAL)

See also: novas_diff_tcb(); novas_diff_time()

Since: 1.1

Author: Attila Kovacs

References novas_diff_time().

◆ novas_diff_time() ◆ novas_dms_degrees() double novas_dms_degrees ( const char *restrict dms )

Returns the decimal degrees for a DMS string specification. The degree, (arc)minute, and (arc)second components may be separated by spaces, tabs, colons :, or a combination thereof. Additionally, the degree and minutes may be separated by the letter d, and the minutes and seconds may be separated by m or a single quote ‘’‘. The seconds may be followed by 's’ or double quote ". Finally, the leading or trailing component may additionally be a standalone upper-case letter 'N', 'E', 'S', or 'W' or the words 'North', 'East', 'South', or 'West' (case insensitive), signifying a compass direction.

There is no enforcement on the range of angles that can be represented in this way. Any finite angle is parseable, even if it is outside its conventional range, such as +- 90 degrees N/S.

For example, all of the lines below are valid specifications:

 -179:59:59.999
 -179d 59m 59.999s
 -179 59' 59.999
 179:59:59.999S
 179 59 59.999 W
 179 59 59.999 west
 179_59_59.999__S
 W 179 59 59
 North 179d 59m

At least the leading two components (degrees and arcminutes) are required. If the arcseconds are ommitted, they will be assumed zero, i.e. 179:59 is the same as 179:59:00.000.

NOTES:

To see if the string was fully parsed when returning a valid (non-NAN) value, you can check errno: it should be zero (0) if all non-whitespace characters have been parsed from the input string, or else EINVAL if the parsed value used only the leading part of the string.

Parameters: dms String specifying degrees, minutes, and seconds, which correspond to an angle. Angles in any range are permitted, but the minutes and seconds must be >=0 and <60.

Returns: [deg] Corresponding decimal angle value, or else NAN if there was an error parsing the string (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_str_degrees(); novas_parse_dms(); novas_hms_hours()

References novas_parse_dms().

◆ novas_e2h_offset() int novas_e2h_offset ( double dra, double ddec, double pa, double *restrict daz, double *restrict del )

Converts coordinate offsets, from the local equatorial system to local horizontal offsets. Converting between local flat projections and spherical coordinates usually requires a WCS projection.

REFERENCES:

Calabretta, M.R., & Greisen, E.W., (2002), Astronomy & Astrophysics, 395, 1077-1122.

Parameters: dra [arcsec] Projected ffset position in the apparent true-of-date R.A. direction. E.g. The projected offset between two RA coordinates at a same reference declination, is δRA = (RA2 - RA1) * cos(Dec₀) ddec [arcsec] Projected offset position in the apparent true-of-date declination direction. pa [deg] Parallactic Angle [out] daz [arcsec] Output offset position in the local azimuth direction. It can be a pointer to one of the input coordinates, or NULL if not required. [out] del [arcsec] Output offset position in the local elevation direction. It can be a pointer to one of the input coordinates, or NULL if not required.

Returns: 0

Since: 1.3

Author: Attila Kovacs

See also: novas_h2e_offset(); novas_epa()

References novas_h2e_offset().

◆ novas_epa() double novas_epa ( double ha, double dec, double lat )

Returns the equatorial Parallactic Angle (PA) calculated for an R.A./Dec location of the sky at a given sidereal time. The PA is the angle between the local horizontal coordinate directions and the local true-of-date equatorial coordinate directions, at the given location and time. The polar wobble is not included in the calculation.

The Parallactic Angle is sometimes referrred to as the Vertical Position Angle (VPA). Both define the same quantity.

Parameters: ha [h] Hour angle (LST - RA) i.e., the difference between the Local (apparent) Sidereal Time and the apparent (true-of-date) Right Ascension of observed source. dec [deg] Apparent (true-of-date) declination of observed source lat [deg] Geodetic latitude of observer

Returns: [deg] Parallactic Angle (PA). I.e., the clockwise position angle of the elevation direction w.r.t. the declination axis in the equatorial system. Same as the clockwise position angle of the declination direction w.r.t. the elevation axis, in the horizontal system.

Since: 1.3

Author: Attila Kovacs

See also: novas_hpa(); novas_lst(); novas_e2h_offset()

◆ novas_epoch() double novas_epoch ( const char *restrict system )

Returns the Julian day corresponding to an astronomical coordinate epoch.

Parameters: system Coordinate system, e.g. "ICRS", "B1950.0", "J2000.0", "FK4", "FK5", "1950", "2000", or "HIP". In general, any Besselian or Julian year epoch can be used by year (e.g. "B1933.193" or "J2022.033"), or else the fixed values listed. If 'B' or 'J' is ommitted in front of the epoch year, then Besselian epochs are assumed prior to 1984.0.

Returns: [day] The Julian day corresponding to the given coordinate epoch, or else NAN if the input string is NULL or the input is not recognised as a coordinate epoch specification (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: make_cat_object_sys(); make_redshifted_object_sys(); transform_cat(); precession(); NOVAS_SYSTEM_ICRS; NOVAS_SYSTEM_B1950; NOVAS_SYSTEM_J2000; NOVAS_SYSTEM_HIP

References NOVAS_JD_B1950, NOVAS_JD_HIP, NOVAS_JD_J2000, NOVAS_SYSTEM_FK4, NOVAS_SYSTEM_FK5, NOVAS_SYSTEM_HIP, and NOVAS_SYSTEM_ICRS.

◆ novas_equ_sep() double novas_equ_sep ( double ra1, double dec1, double ra2, double dec2 )

Returns the angular separation of two equatorial locations on a sphere.

Parameters: ra1 [h] right ascension of first location dec1 [deg] declination of first location ra2 [h] right ascension of second location dec2 [deg] declination of second location

Returns: [deg] the angular separation of the two locations.

Since: 1.3

Author: Attila Kovacs

See also: novas_sep(); novas_sun_angle(); novas_moon_angle()

References novas_sep().

◆ novas_equ_track()

Calculates equatorial tracking position and motion (first and second time derivatives) for the specified source in the given observing frame. The position and its derivatives are calculated via the more precise IAU2006 method, and CIRS.

Parameters: source Observed source frame Observing frame, defining the observer location and astronomical time of observation. dt [s] Time step used for calculating derivatives. [out] track Output tracking parameters to populate

Returns: 0 if successful, or else -1 if any of the pointer arguments are NULL, or else an error code from cio_ra() or from novas_sky_pos().

Since: 1.3

Author: Attila Kovacs

See also: novas_hor_track(); novas_track_pos()

References cio_ra(), sky_pos::dec, sky_pos::dis, novas_timespec::fjd_tt, NOVAS_CIRS, novas_make_frame(), novas_sky_pos(), novas_v2z(), sky_pos::ra, sky_pos::rv, and SKY_POS_INIT.

◆ novas_frame_lst() double novas_frame_lst ( const novas_frame *restrict frame )

Returns the Local (apparent) Sidereal Time for an observing frame of an Earth-bound observer.

Parameters: frame Observer frame, defining the location and time of observation

Returns: [h] The LST for an Earth-bound observer [0.0–24.0), or NAN otherwise. If NAN is returned errno will indicate the type of error.

Since: 1.3

Author: Attila Kovacs

References NOVAS_AIRBORNE_OBSERVER, and NOVAS_OBSERVER_ON_EARTH.

◆ novas_geom_posvel()

Calculates the geometric position and velocity vectors, relative to the observer, for a source in the given observing frame, in the specified coordinate system of choice. The geometric position includes proper motion, and for solar-system bodies it is antedated for light travel time, so it effectively represents the geometric position as seen by the observer. However, the geometric does not include aberration correction, nor gravitational deflection.

If you want apparent positions, which account for aberration and gravitational deflection, use novas_skypos() instead.

You can also use novas_transform_vector() to convert the output position and velocity vectors to a dfferent coordinate system of choice afterwards if you want the results expressed in more than one coordinate system.

It implements the same geometric transformations as place() but at a reduced computational cost. See place() for references.

NOTES:

If sys is NOVAS_TOD (true equator and equinox of date), the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C place() for that system. To obtain more precise TOD coordinates, set sys to NOVAS_CIRS here, and follow with cirs_to_tod() after.
As of SuperNOVAS v1.3, the returned velocity vector is a proper observer-based velocity measure. In prior releases, and in NOVAS C 3.1, this was inconsistent, with pseudo LSR-based measures being returned for catalog sources.

Parameters: source Pointer to a celestial source data structure that is observed. Catalog sources should have coordinates and properties in ICRS. You can use transform_cat() to convert catalog entries to ICRS as necessary. frame Observer frame, defining the location and time of observation sys The coordinate system in which to return positions and velocities. [out] pos [AU] Calculated geometric position vector of the source relative to the observer location, in the designated coordinate system. It may be NULL if not required. [out] vel [AU/day] The calculated velocity vector of the source relative to the observer in the designated coordinate system. It must be distinct from the pos output vector, and may be NULL if not required.

Returns: 0 if successful, or else -1 if any of the arguments is invalid, 50–70 error is 50 + error from light_time2().

See also: novas_geom_to_app(); novas_sky_pos(); novas_transform_vector(); place(); cirs_to_tod()

Since: 1.1

Author: Attila Kovacs

References bary2obs(), d_light(), light_time2(), NOVAS_CATALOG_OBJECT, NOVAS_FULL_ACCURACY, novas_get_time(), NOVAS_JD_J2000, NOVAS_PLANET, NOVAS_REDUCED_ACCURACY, NOVAS_TDB, proper_motion(), and starvectors().

◆ novas_geom_to_app()

Converts an geometric position in ICRS to an apparent position on sky, by applying appropriate corrections for aberration and gravitational deflection for the observer's frame. Unlike place() the output reports the distance calculated from the parallax for sidereal sources. The radial velocity of the output is set to NAN (if needed use novas_sky_pos() instead).

Parameters: frame The observer frame, defining the location and time of observation pos [AU] Geometric position of source in ICRS coordinates sys The coordinate system in which to return the apparent sky location [out] out Pointer to the data structure which is populated with the calculated apparent location in the designated coordinate system. It may be the same pounter as the input position.

Returns: 0 if successful, or an error from grav_def2(), or else -1 (errno will indicate the type of error).

See also: novas_sky_pos(); novas_app_to_geom(); novas_app_to_hor(); novas_geom_posvel()

Since: 1.1

Author: Attila Kovacs

References grav_planets(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, novas_vlen(), and vector2radec().

◆ novas_get_debug_mode()

Returns the current, thread-local, mode for reporting errors encountered (and traces).

Returns: The current debug mode in the calling thread.

Since: 1.0

Author: Attila Kovacs

See also: novas_debug()

◆ novas_get_split_time()

Returns the fractional Julian date of an astronomical time in the specified timescale, as an integer and fractional part. The two-component split of the time allows for absolute precisions at the picosecond level, as opposed to novas_set_time(), whose precision is limited to a few microseconds typically.

The accuracy of Barycentric Time measures (TDB and TCB) relative to other time measures is limited by the precision of the tbd2tt() implemenation, to around 10 μs.

REFERENCES:

IAU 1991, RECOMMENDATION III. XXIst General Assembly of the International Astronomical Union. Retrieved 6 June 2019.
IAU 2006 resolution 3, see Recommendation and footnotes, note 3.
Fairhead, L. & Bretagnon, P. (1990) Astron. & Astrophys. 229, 240.
Kaplan, G. (2005), US Naval Observatory Circular 179.
https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html
https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems

Parameters: time Pointer to the astronomical time specification data structure. timescale The astronomical time scale in which the returned Julian Date is to be provided [out] ijd [day] The integer part of the Julian date in the requested timescale. It may be NULL if not required.

Returns: [day] The fractional part of the Julian date in the requested timescale or NAN is the time argument is NULL (ijd will be set to -1 also).

See also: novas_set_split_time(); novas_get_time()

Since: 1.1

Author: Attila Kovacs

References NOVAS_GPS, NOVAS_TAI, NOVAS_TCB, NOVAS_TCG, NOVAS_TDB, NOVAS_TT, NOVAS_UT1, and NOVAS_UTC.

◆ novas_get_time()

Returns the fractional Julian date of an astronomical time in the specified timescale. The returned time is accurate to a few μs (microsecond) due to the inherent precision of the double-precision result. For higher precision applications you may use novas_get_split_time() instead, which has an inherent accuracy at the picosecond level.

Parameters: time Pointer to the astronomical time specification data structure. timescale The astronomical time scale in which the returned Julian Date is to be provided

Returns: [day] The Julian date in the requested timescale.

See also: novas_set_time(); novas_get_split_time()

Since: 1.1

Author: Attila Kovacs

References novas_get_split_time().

◆ novas_get_unix_time() time_t novas_get_unix_time ( const novas_timespec *restrict time, long *restrict nanos )

Returns the UNIX time for an astronomical time instant.

Parameters: time Pointer to the astronomical time specification data structure. [out] nanos [ns] UTC sub-second component. It may be NULL if not required.

Returns: [s] The integer UNIX time, or -1 if the input time is NULL.

See also: novas_set_unix_time(); novas_get_time()

Since: 1.1

Author: Attila Kovacs

References novas_get_split_time(), and NOVAS_UTC.

◆ novas_h2e_offset() int novas_h2e_offset ( double daz, double del, double pa, double *restrict dra, double *restrict ddec )

Converts coordinate offsets, from the local horizontal system to local equatorial offsets. Converting between local flat projections and spherical coordinates usually requires a WCS projection.

REFERENCES:

Calabretta, M.R., & Greisen, E.W., (2002), Astronomy & Astrophysics, 395, 1077-1122.

Parameters: daz [arcsec] Projected offset position in the azimuth direction. The projected offset between two azimuth positions at the same reference elevation is δAz = (Az2 - Az1) * cos(El₀). del [arcsec] projected offset position in the elevation direction pa [deg] Parallactic Angle [out] dra [arcsec] Output offset position in the local true-of-date R.A. direction. It can be a pointer to one of the input coordinates, or NULL if not required. [out] ddec [arcsec] Output offset position in the local true-of-date declination direction. It can be a pointer to one of the input coordinates, or NULL if not required.

Returns: 0

Since: 1.3

Author: Attila Kovacs

See also: novas_e2h_offset(); novas_hpa()

◆ novas_hms_hours() double novas_hms_hours ( const char *restrict hms )

Returns the decimal hours for a HMS string specification. The hour, minute, and second components may be separated by spaces, tabs, colons :, or a combination thereof. Additionally, the hours and minutes may be separated by the letter h, and the minutes and seconds may be separated by m or a single quote ‘’‘. The seconds may be followed by 's’ or double quote ".

There is no enforcement on the range of hours that can be represented in this way. Any finite angle is parseable, even if it is outside its conventional range of 0-24h.

For example, all of the lines below specify the same time:

 23:59:59.999
 23h 59m 59.999s
 23h59'59.999
 23 59 59.999
 23 59
 23h

At least the leading two components (hours and minutes) are required. If the seconds are ommitted, they will be assumed zero, i.e. 23:59 is the same as 23:59:00.000.

NOTES:

To see if the string was fully parsed when returning a valid (non-NAN) value, you can check errno: it should be zero (0) if all non-whitespace characters have been parsed from the input string, or else EINVAL if the parsed value used only the leading part of the string.

Parameters: hms String specifying hours, minutes, and seconds, which correspond to a time between 0 and 24 h. Time in any range is permitted, but the minutes and seconds must be >=0 and <60.

Returns: [hours] Corresponding decimal time value, or else NAN if there was an error parsing the string (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_str_hours(); novas_parse_hms(); novas_dms_degrees()

References novas_parse_hms().

◆ novas_hor_to_app()

Converts an observed azimuth and elevation coordinate to right ascension (R.A.) and declination coordinates expressed in the coordinate system of choice. The observer must be located on the surface of Earth, or else the call will return with an error. The caller may optionally supply a refraction model of choice to calculate an appropriate elevation angle that includes a refraction correction for Earth's atmosphere. If no such model is provided, the provided elevation value will be assumed to be an astrometric elevation without a refraction correction.

Parameters: frame Observer frame, defining the time and place of observation (on Earth). az [deg] Observed azimuth angle. It may be NULL if not required. el [deg] Observed elevation angle. It may be NULL if not required. ref_model An appropriate refraction model, or NULL to assume unrefracted elevation. Depending on the refraction model, you might want to make sure that the weather parameters were set when the observing frame was defined. sys Astronomical coordinate system in which the output is R.A. and declination values are to be calculated. [out] ra [h] Calculated apparent right ascension (R.A.) coordinate [out] dec [deg] Calculated apparent declination coordinate

Returns: 0 if successful, or else an error from itrs_to_tod() or itrs_to_cirs(), or -1 (errno will indicate the type of error).

See also: novas_app_to_hor(); novas_app_to_geom(); novas_standard_refraction(); novas_optical_refraction(); novas_radio_refraction(); novas_wave_refraction()

Since: 1.1

Author: Attila Kovacs

References novas_timespec::fjd_tt, hor_to_itrs(), novas_timespec::ijd_tt, NOVAS_AIRBORNE_OBSERVER, NOVAS_CIRS, NOVAS_GCRS, NOVAS_ICRS, NOVAS_ITRS, NOVAS_J2000, NOVAS_MOD, NOVAS_OBSERVER_ON_EARTH, NOVAS_REFRACT_OBSERVED, NOVAS_TIRS, NOVAS_TOD, spin(), vector2radec(), wobble(), WOBBLE_ITRS_TO_PEF, and WOBBLE_ITRS_TO_TIRS.

◆ novas_hor_track()

Calculates horizontal tracking position and motion (first and second time derivatives) for the specified source in the given observing frame. The position and its derivatives are calculated via the more precise IAU2006 method, and CIRS, and then converted to local horizontal coordinates using the specified refraction model (if any).

Parameters: source Observed source frame Observing frame, defining the observer location and astronomical time of observation. ref_model Refraction model to use, or NULL for an unrefracted track. [out] track Output tracking parameters to populate

Returns: 0 if successful, or else -1 if any of the pointer arguments are NULL, or else an error code from cio_ra() or from novas_sky_pos(), or from novas_app_hor().

Since: 1.3

Author: Attila Kovacs

See also: novas_equ_track(); novas_track_pos()

References cio_ra(), sky_pos::dec, sky_pos::dis, novas_timespec::fjd_tt, NOVAS_AIRBORNE_OBSERVER, novas_app_to_hor(), NOVAS_CIRS, novas_make_frame(), NOVAS_OBSERVER_ON_EARTH, novas_sky_pos(), NOVAS_TOD, novas_v2z(), sky_pos::ra, sky_pos::rv, and SKY_POS_INIT.

◆ novas_hpa() double novas_hpa ( double az, double el, double lat )

Returns the horizontal Parallactic Angle (PA) calculated for a gorizontal Az/El location of the sky. The PA is the angle between the local horizontal coordinate directions and the local true-of-date equatorial coordinate directions at the given location. The polar wobble is not included in the calculation.

The Parallactic Angle is sometimes referrred to as the Vertical Position Angle (VPA). Both define the same quantity.

Parameters: az [deg] Azimuth angle el [deg] Elevation angle lat [deg] Geodetic latitude of observer

Returns: [deg] Parallactic Angle (PA). I.e., the clockwise position angle of the declination direction w.r.t. the elevation axis in the horizontal system. Same as the the clockwise position angle of the elevation direction w.r.t. the declination axis in the equatorial system.

Since: 1.3

Author: Attila Kovacs

See also: novas_epa(); novas_h2e_offset()

◆ novas_inv_refract()

Computes the reverse atmospheric refraction for a given refraction model. Thus if a refraction model takes observed elevation as an input, the reverse refraction takes astrometric elevation as its input, and vice versa.

Parameters: model The original refraction model jd_tt [day] Terrestrial Time (TT) based Julian data of observation loc Pointer to structure defining the observer's location on earth, and local weather type Refraction type to use for the original model: NOVAS_REFRACT_OBSERVED (-1) or NOVAS_REFRACT_ASTROMETRIC (0). el0 [deg] input elevation for the inverse refraction model.

Returns: [deg] Estimated refraction, or NAN if there was an error (it should also set errno to indicate the type of error).

See also: refract_astro(); itrs_to_hor()

Since: 1.1

Author: Attila Kovacs

References novas_inv_max_iter, and NOVAS_REFRACT_OBSERVED.

◆ novas_invert_transform()

Inverts a novas coordinate transformation matrix.

Parameters: transform Pointer to a coordinate transformation matrix. [out] inverse Pointer to a coordinate transformation matrix to populate with the inverse transform. It may be the same as the input.

Returns: 0 if successful, or else -1 if the was an error (errno will indicate the type of error).

See also: novas_make_transform()

Since: 1.1

Author: Attila Kovacs

References novas_transform::matrix.

◆ novas_iso_timestamp() int novas_iso_timestamp ( const novas_timespec *restrict time, char *restrict dst, int maxlen )

Prints a UTC-based ISO timestamp to millisecond precision to the specified string buffer. E.g.:

 2025-01-26T21:32:49.701Z

NOTES:

As per the ISO 8601 specification, the timestamp uses the Gregorian date, even for dates prior to the Gregorian calendar reform of 15 October 1582 (i.e. proleptic Gregorian dates).
B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

Parameters: time Pointer to the astronomical time specification data structure. [out] dst Output string buffer. At least 25 bytes are required for a complete timestamp with termination. maxlen The maximum number of characters that can be printed into the output buffer, including the string termination. If the full ISO timestamp is longer than maxlen, then it will be truncated to fit in the allotted space, including a termination character.

Returns: the number of characters printed into the string buffer, not including the termination. As such it is at most maxlen - 1.

Since: 1.3

Author: Attila Kovacs

See also: novas_timestamp(); novas_parse_iso_date()

References novas_get_split_time(), NOVAS_GREGORIAN_CALENDAR, and NOVAS_UTC.

◆ novas_jd_from_date() double novas_jd_from_date ( enum novas_calendar_type calendar, int year, int month, int day, double hour )

Returns the Julian day for a given calendar date. Input time value can be based on any astronomical time scale (UTC, UT1, TT, etc.) - output Julian date will have the same basis.

The input date is the conventional calendar date, affected by the Gregorian calendar reform of 1582. Thus, the input date is for the Gregorian calendar for dates starting 15 October 1582, and for the Julian (Roman) calendar (introduced in 45 B.C.) for dates prior to that.

NOTES:

B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.
Added argument range checking in v1.3.0, returning NAN if the month or day are out of the normal range (for a leap year).

REFERENCES:

Fliegel, H. & Van Flandern, T. Comm. of the ACM, Vol. 11, No. 10, October 1968, p. 657.

Parameters: calendar The type of calendar to use: NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_GREGORIAN_CALENDAR, or NOVAS_ROMAN_CALENDAR. year [yr] Calendar year. B.C. years can be simply represented as negative years, e.g. 1 B.C. as -1. month [month] Calendar month [1:12] day [day] Day of month [1:31] hour [hr] Hour of day [0:24]

Returns: [day] the fractional Julian day for the input calendar date, ot NAN if the calendar is invalid or the month or day components are out of range.

Since: 1.3

Author: Attila Kovacs

See also: novas_jd_to_date(); get_utc_to_tt(); get_ut1_to_tt(); tt2tdb()

References NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_GREGORIAN_CALENDAR, NOVAS_JD_START_GREGORIAN, and NOVAS_ROMAN_CALENDAR.

◆ novas_jd_to_date() int novas_jd_to_date ( double tjd, enum novas_calendar_type calendar, int *restrict year, int *restrict month, int *restrict day, double *restrict hour )

This function will compute a broken down date on the specified calendar for given the Julian day input. Input Julian day can be based on any astronomical time scale (UTC, UT1, TT, etc.) - output time value will have same basis.

NOTES:

B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

REFERENCES:

Fliegel, H. & Van Flandern, T. Comm. of the ACM, Vol. 11, No. 10, October 1968, p. 657.

Parameters: tjd [day] Julian day. calendar The type of calendar to use: NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_GREGORIAN_CALENDAR, or NOVAS_ROMAN_CALENDAR. [out] year [yr] Calendar year. B.C. years are represented as negative values, e.g. -1 corresponds to 1 B.C. It may be NULL if not required. [out] month [month] Calendar month [1:12]. It may be NULL if not required. [out] day [day] Day of the month [1:31]. It may be NULL if not required. [out] hour [h] Hour of day [0:24]. It may be NULL if not required.

Returns: 0 if successful, or else -1 if the calendar is invalid (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_jd_from_date(); get_utc_to_tt(); get_ut1_to_tt(); tt2tdb()

References NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_GREGORIAN_CALENDAR, NOVAS_JD_START_GREGORIAN, and NOVAS_ROMAN_CALENDAR.

◆ novas_los_to_xyz() int novas_los_to_xyz ( const double * los, double lon, double lat, double * xyz )

Converts a 3D line-of-sight vector (δφ, δθ δr) to a rectangular equatorial (δx, δy, δz) vector.

Parameters: los [arb.u.] Line-of-sight 3-vector (δφ, δθ δr). lon [deg] Line-of-sight longitude. lat [deg] Line-of-sight latitude. [out] xyz [arb.u.] Output rectangular equatorial 3-vector (δx, δy, δz), in the same units as the input. It may be the same vector as the input.

Returns: 0 if successful, or else -1 if either vector argument is NULL (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_xyz_to_los(); novas_uvw_to_xyz()

◆ novas_lsr_to_ssb_vel() double novas_lsr_to_ssb_vel ( double epoch, double ra, double dec, double vLSR )

Returns a Solar System Baricentric (SSB) radial velocity for a radial velocity that is referenced to the Local Standard of Rest (LSR). Internally, NOVAS always uses barycentric radial velocities, but it is just as common to have catalogs define radial velocities referenced to the LSR.

The SSB motion w.r.t. the barycenter is assumed to be (11.1, 12.24, 7.25) km/s in ICRS (Shoenrich et al. 2010).

REFERENCES:

Ralph Schoenrich, James Binney, Walter Dehnen, Monthly Notices of the Royal Astronomical Society, Volume 403, Issue 4, April 2010, Pages 1829–1833, https://doi.org/10.1111/j.1365-2966.2010.16253.x

Parameters: epoch [yr] Coordinate epoch in which the coordinates and velocities are defined. E.g. 2000.0. ra [h] Right-ascenscion of source at given epoch. dec [deg] Declination of source at given epoch. vLSR [km/s] radial velocity defined against the Local Standard of Rest (LSR), at given epoch.

Returns: [km/s] Equivalent Solar-System Barycentric radial velocity.

Since: 1.3

Author: Attila Kovacs

See also: make_cat_entry(); novas_ssb_to_lsr_vel()

References NOVAS_JD_J2000, precession(), and radec2vector().

◆ novas_make_frame()

Sets up a observing frame for a specific observer location, time of observation, and accuracy requirement. The frame is initialized using the currently configured planet ephemeris provider function (see set_planet_provider() and set_planet_provider_hp()), and in case of reduced accuracy mode, the currently configured IAU nutation model provider (see set_nutation_lp_provider()).

Note, that to construct full accuracy frames, you will need a high-precision ephemeris provider for the major planets (not just the default Earth/Sun), as without it, gravitational bending around massive plannets cannot be accounted for, and therefore μas accuracy cannot be ensured, in general. Attempting to construct a high-accuracy frame without a high-precision ephemeris provider for the major planets will result in an error in the 10–40 range from the required ephemeris() call.

NOTES:

This function expects the Earth polar wobble parameters to be defined on a per-frame basis and will not use the legacy global (undated) orientation parameters set via cel_pole().

Parameters: accuracy Accuracy requirement, NOVAS_FULL_ACCURACY (0) for the utmost precision or NOVAS_REDUCED_ACCURACY (1) if ~1 mas accuracy is sufficient. obs Observer location time Time of observation dx [mas] Earth orientation parameter, polar offset in x, e.g. from the IERS Bulletins. (The global, undated value set by cel_pole() is not not used here.) You can use 0.0 if sub-arcsecond accuracy is not required. dy [mas] Earth orientation parameter, polar offset in y, e.g. from the IERS Bulletins. (The global, undated value set by cel_pole() is not not used here.) You can use 0.0 if sub-arcsecond accuracy is not required. [out] frame Pointer to the observing frame to configure.

Returns: 0 if successful, 10–40: error is 10 + the error from ephemeris(), 40–50: error is 40 + the error from geo_posvel(), 50–80: error is 50 + the error from sidereal_time(), 80–90 error is 80 + error from cio_location(), 90–100 error is 90 + error from cio_basis(). or else -1 if there was an error (errno will indicate the type of error).

See also: novas_change_observer(); novas_sky_pos(); novas_geom_posvel(); novas_make_transform(); set_planet_provider(); set_planet_provider_hp(); set_nutation_lp_provider()

Since: 1.1

Author: Attila Kovacs

References novas_frame::accuracy, novas_frame::deps0, novas_frame::dpsi0, novas_frame::dx, novas_frame::dy, novas_frame::earth_pos, novas_frame::earth_vel, novas_frame::ee, ee_ct(), ephemeris(), novas_frame::era, era(), EROT_GST, novas_timespec::fjd_tt, novas_frame::gst, novas_timespec::ijd_tt, mean_obliq(), novas_frame::mobl, NOVAS_BARYCENTER, novas_change_observer(), NOVAS_EARTH_INIT, novas_get_split_time(), NOVAS_JD_J2000, NOVAS_OBSERVER_PLACES, NOVAS_REDUCED_ACCURACY, NOVAS_SUN_INIT, NOVAS_TRUE_EQUINOX, NOVAS_UT1, nutation_angles(), sidereal_time(), novas_frame::state, novas_frame::sun_pos, novas_frame::sun_vel, novas_frame::time, novas_frame::tobl, tt2tdb(), novas_timespec::ut1_to_tt, and observer::where.

◆ novas_make_transform()

Calculates a transformation matrix that can be used to convert positions and velocities from one coordinate reference system to another.

Parameters: frame Observer frame, defining the location and time of observation from_system Original coordinate reference system to_system New coordinate reference system [out] transform Pointer to the transform data structure to populate.

Returns: 0 if successful, or else -1 if there was an error (errno will indicate the type of error).

See also: novas_transform_vector(); novas_transform_sky_pos(); novas_invert_transform(); novas_geom_posvel(); novas_app_to_geom()

Since: 1.1

Author: Attila Kovacs

References novas_frame::era, novas_transform::frame, novas_transform::from_system, novas_frame::gcrs_to_cirs, novas_frame::icrs_to_j2000, novas_matrix::M, novas_transform::matrix, NOVAS_CIRS, NOVAS_GCRS, NOVAS_ICRS, NOVAS_ITRS, NOVAS_J2000, NOVAS_MOD, NOVAS_REFERENCE_SYSTEMS, NOVAS_TIRS, NOVAS_TOD, novas_frame::nutation, novas_frame::precession, and novas_transform::to_system.

◆ novas_norm_ang() double novas_norm_ang ( double angle )

Returns the normalized angle in the [0:2π) range.

Parameters: angle [rad] an angle in radians.

Returns: [rad] the normalized angle in the [0:2π) range.

Since: 1.0

Author: Attila Kovacs

References TWOPI.

◆ novas_object_sep()

Returns the angular separation of two objects from the observer's point of view. The calculated separation includes light-time corrections, aberration and gravitational deflection for both sources, and thus represents a precise observed separation between the two sources.

Parameters: source1 An observed source source2 Another observed source frame Observing frame, defining the observer location and astronomical time of observation.

Returns: [deg] Apparent angular separation between the two observed sources from the observer's point-of-view.

Since: 1.3

Author: Attila Kovacs

See also: novas_sun_angle(); novas_moon_angle(); novas_sep()

References sky_pos::dec, sky_pos::dis, novas_equ_sep(), NOVAS_GCRS, novas_sky_pos(), sky_pos::ra, and SKY_POS_INIT.

◆ novas_offset_time()

Increments the astrometric time by a given amount.

Parameters: time Original time specification seconds [s] Seconds to add to the original [out] out New incremented time specification. It may be the same as the input.

Returns: 0 if successful, or else -1 if either the input or the output is NULL (errno will be set to EINVAL).

See also: novas_set_time(); novas_diff_time()

Since: 1.1

Author: Attila Kovacs

References novas_timespec::fjd_tt, and novas_timespec::ijd_tt.

◆ novas_optical_refraction()

Returns an optical refraction correction using the weather parameters defined for the observer location.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian data of observation (unused in this implementation of RefractionModel) loc Pointer to structure defining the observer's location on earth, and local weather type Whether the input elevation is observed or astrometric: NOVAS_REFRACT_OBSERVED (-1) or NOVAS_REFRACT_ASTROMETRIC (0). el [deg] Astrometric (unrefracted) source elevation

Returns: [arcsec] Estimated refraction, or NAN if there was an error (it should also set errno to indicate the type of error).

See also: novas_app_to_hor(); novas_optical_refraction(); NOVAS_STANDARD_ATMOSPHERE(); refract(); refract_astro()

References NOVAS_WEATHER_AT_LOCATION.

◆ novas_parse_date() double novas_parse_date ( const char *restrict date, char **restrict tail )

Parses an astronomical date/time string into a Julian date specification.

The date must be YMD-type with full year, followed the month (numerical or name or 3-letter abbreviation), and the day. The components may be separated by dash -, underscore _, dot ., slash '/', or spaces/tabs, or any combination thereof. The date may be followed by a time specification in HMS format, separated from the date by the letter T or t, or spaces, comma ,, or semicolon ;, or underscore _ or a combination thereof. Finally, the time may be followed by the letter Z, or z (for UTC) or else {+/-}HH[:[MM]] time zone specification.

For example:

 2025-01-26
 2025 January 26
 2025_Jan_26
 2025-01-26T19:33:08Z
 2025.01.26T19:33:08
 2025 1 26 19h33m28.113
 2025/1/26 19:33:28+02
 2025-01-26T19:33:28-0600
 2025 Jan 26 19:33:28+05:30

are all valid dates that can be parsed.

NOTES:

This function assumes Gregorian dates after their introduction on 1582 October 15, and Julian/Roman dates before that, as was the convention of the time. I.e., the day before of the introduction of the Gregorian calendar reform is 1582 October 4. I.e., you should not use this function with ISO 8601 timestamps containing dates prior to 1582 October 15 (for such date you may use novas_parse_iso_date() instead).
B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

Parameters: date The astronomical date specification, possibly including time and timezone, in a standard format. The date is assumed to be in the astronomical calendar of date, which differs from ISO 8601 timestamps for dates prior to the Gregorian calendar reform of 1582 October 15 (otherwise, the two are identical). [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed time.

Returns: [day] The Julian Day corresponding to the string date/time specification or NAN if the string is NULL or if it does not specify a date/time in the expected format.

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_iso_date(); novas_parse_date_format(); novas_date(); novas_date_scale(); novas_timescale_for_string(); novas_iso_timestamp(); novas_timestamp()

References NOVAS_ASTRONOMICAL_CALENDAR, novas_parse_date_format(), and NOVAS_YMD.

◆ novas_parse_date_format()

Parses a calndar date/time string, expressed in the specified type of calendar, into a Julian day (JD). The date must be composed of a full year (e.g. 2025), a month (numerical or name or 3-letter abbreviation, e.g. "01", "1", "January", or "Jan"), and a day (e.g. "08" or "8"). The components may be separated by dash -, underscore _, dot ., slash '/', or spaces/tabs, or any combination thereof. The components will be parsed in the specified order.

The date may be followed by a time specification in HMS format, separated from the date by the letter T or t, or spaces, comma ,, or semicolon ; or underscore '_', or a combination thereof. Finally, the time may be followed by the letter Z, or z (for UTC) or else by a {+/-}HH[:[MM]] time zone specification.

For example, for format NOVAS_YMD, all of the following strings may specify the date:

 2025-01-26
 2025 January 26
 2025_Jan_26
 2025-01-26T19:33:08Z
 2025.01.26T19:33:08
 2025 1 26 19h33m28.113
 2025/1/26 19:33:28+02
 2025-01-26T19:33:28-0600
 2025 Jan 26 19:33:28+05:30

are all valid dates that can be parsed.

If your date format cannot be parsed with this function, you may parse it with your own function into year, month, day, and decimal hour-of-day components, and use julian_date() with those.

NOTES:

B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

Parameters: calendar The type of calendar to use: NOVAS_ASTRONOMICAL_CALENDAR, NOVAS_GREGORIAN_CALENDAR, or NOVAS_ROMAN_CALENDAR. format Expected order of date components: NOVAS_YMD, NOVAS_DMY, or NOVAS_MDY. date The date specification, possibly including time and timezone, in the specified standard format. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed time.

Returns: [day] The Julian Day corresponding to the string date/time specification or NAN if the string is NULL or if it does not specify a date/time in the expected format.

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_date(); novas_parse_iso_date(); novas_timescale_for_string(); novas_iso_timestamp(); julian_date()

References novas_debug(), NOVAS_DEBUG_OFF, NOVAS_DMY, novas_get_debug_mode(), novas_jd_from_date(), NOVAS_MDY, novas_parse_hms(), and NOVAS_YMD.

◆ novas_parse_degrees() double novas_parse_degrees ( const char *restrict str, char **restrict tail )

Parses an angle in degrees from a string that contains either a decimal degrees or else a broken-down DMS representation.

The decimal representation may be followed by a unit designator: "d", "dg", "deg", "degree", or "degrees", which will be parsed case-insensitively also, if present.

Both DMS and decimal values may start or end with a compass direction: such as an upper-case letter N, E, S, or W, or else the case-insensitive words 'North', 'East', 'South' or 'West'.

There is no enforcement on the range of angles that can be represented in this way. Any finite angle is parseable, even if it is outside its conventional range, such as +- 90 degrees N/S.

A few examples of angles that may be parsed:

 -179:59:59.999
 -179d 59m 59.999s
 179 59' 59.999" S
 179 59 S
 -179.99999d
 -179.99999
 179.99999W
 179.99999 West
 179.99999 deg S
 W 179.99999d
 North 179d 59m
 east 179.99 degrees

Parameters: str The input string that specified an angle either as decimal degrees or as a broken down DMS speficication. The decimal value may be followed by the letter d immediately. And both the decimal and DMS representation may be ended with a compass direction marker, N, E, S, or W. See more in novas_parse_dms() on acceptable DMS specifications. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed angle.

Returns: [deg] The angle represented by the string, or else NAN if the string could not be parsed into an angle value (errno will indicate the type of error).

Since: 1.3

Author: Attila Kovacs

See also: novas_str_degrees(); novas_parse_dms(); novas_parse_hours()

References novas_debug(), NOVAS_DEBUG_OFF, novas_get_debug_mode(), and novas_parse_dms().

◆ novas_parse_dms() double novas_parse_dms ( const char *restrict dms, char **restrict tail )

Parses the decimal degrees for a DMS string specification. The degree, (arc)minute, and (arc)second components may be separated by spaces, tabs, colons :, underscore _, or a combination thereof. Additionally, the degree and minutes may be separated by the letter d, and the minutes and seconds may be separated by m or a single quote ‘’. The seconds may be followed bysor a double quote"‘. Finally, the leading or trailing component may additionally be a standalone upper-case letter 'N’, 'E', 'S', or 'W' or the words 'North', 'East', 'South', or 'West' (case insensitive), signifying a compass direction.

There is no enforcement on the range of angles that can be represented in this way. Any finite angle is parseable, even if it is outside its conventional range, such as +- 90 degrees N/S.

For example, all of the lines below are valid specifications:

 -179:59:59.999
 -179d 59m 59.999s
 -179 59' 59.999
 179:59:59.999S
 179:59:59.999 W
 179:59:59.999 West
 179_59_59.999__S
 179 59 S
 W 179 59 59
 North 179d 59m

At least the leading two components (degrees and arcminutes) are required. If the arcseconds are ommitted, they will be assumed zero, i.e. 179:59 is the same as 179:59:00.000.

Parameters: dms String specifying degrees, minutes, and seconds, which correspond to an angle. Angles in any range are permitted, but the minutes and seconds must be >=0 and <60. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed time.

Returns: [deg] Corresponding decimal angle value, or else NAN if there was an error parsing the string (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_dms_degrees(); novas_parse_degrees(); novas_print_dms(); novas_parse_hms()

◆ novas_parse_hms() double novas_parse_hms ( const char *restrict hms, char **restrict tail )

Parses the decimal hours for a HMS string specification. The hour, minute, and second components may be separated by spaces, tabs, colons :, underscore _, or a combination thereof. Additionally, the hours and minutes may be separated by the letter h, and the minutes and seconds may be separated by m or a single quote ‘’‘. The seconds may be followed by 's’ or double quote ".

There is no enforcement on the range of hours that can be represented in this way. Any finite angle is parseable, even if it is outside its conventional range of 0-24h.

For example, all of the lines below are valid specifications:

 23:59:59.999
 23h 59m 59.999
 23h59'59.999
 23 59 59.999
 23 59

At least the leading two components (hours and minutes) are required. If the seconds are ommitted, they will be assumed zero, i.e. 23:59 is the same as 23:59:00.000.

Parameters: hms String specifying hours, minutes, and seconds, which correspond to a time between 0 and 24 h. Time in any range is permitted, but the minutes and seconds must be >=0 and <60. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed time.

Returns: [hours] Corresponding decimal time value, or else NAN if there was an error parsing the string (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_hms_hours(); novas_parse_hours(); novas_print_hms(); novas_parse_dms()

◆ novas_parse_hours() double novas_parse_hours ( const char *restrict str, char **restrict tail )

Parses a time or time-like angle from a string that contains either a decimal hours or else a broken-down HMS representation.

The decimal representation may be followed by a unit designator: "h", "hr", "hrs", "hour", or "hours", which will be parsed case-insensitively also, if present.

There is no enforcement on the range of hours that can be represented in this way. Any finite angle is parseable, even if it is outside its conventional range of 0-24h.

A few examples of angles that may be parsed:

 23:59:59.999
 23h 59m 59.999s
 23h59'59.999
 23 59 59.999
 23.999999h
 23.999999 hours
 23.999999

Parameters: str The input string that specified an angle either as decimal hours or as a broken down HMS speficication. The decimal value may be immediately followed by a letter 'h'. See more in novas_parse_hms() on acceptable HMS input specifications. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed angle.

Returns: [h] The time-like value represented by the string, or else NAN if the string could not be parsed into a time-like value (errno will indicate the type of error).

Since: 1.3

Author: Attila Kovacs

See also: novas_str_hours(); novas_parse_hms(); novas_parse_degrees()

References novas_debug(), NOVAS_DEBUG_OFF, novas_get_debug_mode(), and novas_parse_hms().

◆ novas_parse_iso_date() double novas_parse_iso_date ( const char *restrict date, char **restrict tail )

Parses an ISO 8601 timestamp, converting it to a Julian day. It is equivalent to novas_parse_date() for dates after the Gregorian calendar reform of 1582. For earlier dates, ISO timestamps continue to assume the Gregorian calendar (i.e. proleptic Gregorian dates), whereas novas_parse_timestamp() will assume Roman/Julian dates, which were conventionally used before the calendar reform.

NOTES:

B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

Parameters: date The ISO 8601 date specification, possibly including time and timezone, in a standard format. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed time.

Returns: [day] The Julian Day corresponding to the string date/time specification or NAN if the string is NULL or if it does not specify a date/time in the expected format.

Since: 1.3

Author: Attila Kovacs

See also: novas_iso_timestamp(); novas_parse_date()

References NOVAS_GREGORIAN_CALENDAR, novas_parse_date_format(), and NOVAS_YMD.

◆ novas_parse_timescale() enum novas_timescale novas_parse_timescale ( const char *restrict str, char **restrict tail )

Parses the timescale from a string containing a standard abbreviation (case insensitive), and returns the updated parse position after the timescale specification (if any). The following timescale values are recognised: "UTC", "UT", "UT0", "UT1", "GMT", "TAI", "GPS", "TT", "ET", "TCG", "TCB", "TDB".

Parameters: str String specifying an astronomical timescale. Leading white spaces will be skipped over. [out] tail (optional) If not NULL it will be set to the next character in the string after the parsed timescale specification.

Returns: The SuperNOVAS timescale constant (<=0), or else -1 if the string was NULL, empty, or could not be matched to a timescale value (errno will be set to EINVAL also).

Since: 1.3

Author: Attila Kovacs

See also: novas_timescale_for_string(); novas_set_time(); novas_set_split_time(); novas_print_timescale()

References novas_timescale_for_string(), and NOVAS_UTC.

◆ novas_print_dms() int novas_print_dms ( double degrees, enum novas_separator_type sep, int decimals, char *restrict buf, int len )

Prints an angle in degrees as [-]ddd:mm:ss[.S...] into the specified buffer, with up to nanosecond precision.

The degrees component is always printed as 4 characters (up to 3 digits plus optional negative sign), so the output is always aligned. If positive values are expected to be explicitly signed also, the caller may simply put the '+' sign into the leading byte.

NaN and infinite values, are printed as their standard floating-point representations.

Parameters: degrees [deg] angle value sep Type of separators to use between or after components. If the separator value is outside of the enum range, it will default to using colons. decimals Requested number of decimal places to print for the seconds [0:9]. [out] buf String buffer in which to print DMS string, represented in the [-180:180) degree range. len Maximum number of bytes that may be written into the output buffer, including termination.

Returns: The number of characters actually printed in the buffer, excluding termination, or else -1 if the input buffer is NULL or the length is less than 1 (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_dms(); novas_print_hms()

References MAX_DECIMALS, NOVAS_SEP_COLONS, NOVAS_SEP_SPACES, NOVAS_SEP_UNITS, and NOVAS_SEP_UNITS_AND_SPACES.

◆ novas_print_hms() int novas_print_hms ( double hours, enum novas_separator_type sep, int decimals, char *restrict buf, int len )

Prints a time in hours as hh:mm:ss[.S...] into the specified buffer, with up to nanosecond precision.

NaN and infinite values, are printed as their standard floating-point representations.

Parameters: hours [h] time value sep Type of separators to use between or after components. If the separator value is outside of the enum range, it will default to using colons. decimals Requested number of decimal places to print for the seconds [0:9]. [out] buf String buffer in which to print HMS string, represented in the [0:24) hour range. len Maximum number of bytes that may be written into the output buffer, including termination.

Returns: The number of characters actually printed in the buffer, excluding termination, or else -1 if the input buffer is NULL or the length is less than 1 (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_hms(); novas_print_dms(); novas_timestamp()

References MAX_DECIMALS, NOVAS_SEP_COLONS, NOVAS_SEP_SPACES, NOVAS_SEP_UNITS, and NOVAS_SEP_UNITS_AND_SPACES.

◆ novas_print_timescale() int novas_print_timescale ( enum novas_timescale scale, char *restrict buf )

Prints the standard string representation of the timescale to the specified buffer. The string is terminated after. E.g. "UTC", or "TAI". It will print dates in the Gregorian calendar, which was introduced in was introduced on 15 October 1582 only. Thus the

Parameters: scale The timescale buf String in which to print. It should have at least 4-bytes of available storage.

Returns: the number of characters printed, not including termination, or else -1 if the timescale is invalid or the output buffer is NULL.

Since: 1.3

Author: Attila Kovacs

See also: novas_timestamp(); novas_timescale_for_string()

References NOVAS_GPS, NOVAS_TAI, NOVAS_TCB, NOVAS_TCG, NOVAS_TDB, NOVAS_TT, NOVAS_UT1, and NOVAS_UTC.

◆ novas_radio_refraction()

Atmospheric refraction model for radio wavelengths (Berman & Rockwell 1976). It uses the weather parameters defined for the location, including humidity. As such, make sure the weather data is fully defined, and that the humidity was explicitly set after calling make_on_surface().

Adapted from FORTAN code provided by Berman & Rockwell 1976.

REFERENCES:

Berman, Allan L., and Rockwell, Stephen T. (1976), NASA JPL Technical Report 32-1601

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian data of observation (unused in this implementation of RefractionModel) loc Pointer to structure defining the observer's location on earth, and local weather. Make sure all weather values, including humidity (added in v1.1), are fully populated. type Whether the input elevation is observed or astrometric: NOVAS_REFRACT_OBSERVED (-1) or NOVAS_REFRACT_ASTROMETRIC (0). el [deg] source elevation of the specified type.

Returns: [deg] Estimated refraction, or NAN if there was an error (it should also set errno to indicate the type of error). An error is returned if the location is NULL, or if the weather parameters are way outside of their resonable ranges, or if the elevation is outside the supported [-1:90] range.

See also: novas_optical_refraction(); make_on_surface(); on_surface

References on_surface::humidity, novas_inv_refract(), novas_radio_refraction(), NOVAS_REFRACT_ASTROMETRIC, NOVAS_REFRACT_OBSERVED, on_surface::pressure, and on_surface::temperature.

◆ novas_refract_wavelength() int novas_refract_wavelength ( double microns )

Sets the observing wavelength for which refraction is to be calculated when using a wavelength-depenendent model, such as novas_wave_refraction().

Parameters: microns [μm] Observed wavelength to assume in refraction calculations

Returns: 0 if successful, or else -1 (errno set to EINVAL) if the wavelength invalid (zero, negative, or NaN).

Since: 1.4

Author: Attila Kovacs

See also: novas_wave_refraction(); NOVAS_DEFAULT_WAVELENGTH

◆ novas_rises_above()

Returns the UTC date at which a distant source appears to rise above the specified elevation angle. The calculated time will account for the (slow) motion for Solar-system bodies, and optionally for atmospheric refraction also.

NOTES:

The current implementation is not suitable for calculating the nearest successive rise times for near-Earth objects, at or within the geostationary orbit.
This function calculates the time when the center (not the limb!) of the source rises above the specified elevation threshold. Something to keep in mind for calculating Sun/Moon rise times.

Parameters: el [deg] Elevation angle. source Observed source frame Observing frame, defining the observer location and astronomical time of observation. ref_model Refraction model, or NULL to calculate unrefracted rise time.

Returns: [day] UTC-based Julian date at which the object rises above the specified elevation next after the specified date, or else NAN if the source stays above or below the given elevation for the entire 24-hour period.

Since: 1.3

Author: Attila Kovacs

See also: novas_sets_below(); novas_transit_time()

◆ novas_sep() double novas_sep ( double lon1, double lat1, double lon2, double lat2 )

Returns the angular separation of two locations on a sphere.

Parameters: lon1 [deg] longitude of first location lat1 [deg] latitude of first location lon2 [deg] longitude of second location lat2 [deg] latitude of second location

Returns: [deg] the angular separation of the two locations.

Since: 1.3

Author: Attila Kovacs

See also: novas_equ_sep(); novas_sun_angle(); novas_moon_angle()

◆ novas_set_split_time()

Sets an astronomical time to the split Julian Date value, defined in the specified timescale. The split into the integer and fractional parts can be done in any convenient way. The highest precision is reached if the fractional part is ≤ 1 day. In that case, the time may be specified to picosecond accuracy, if needed.

The accuracy of Barycentric Time measures (TDB and TCB) relative to other time measures is limited by the precision of tbd2tt() implementation, to around 10 μs.

REFERENCES:

IAU 1991, RECOMMENDATION III. XXIst General Assembly of the International Astronomical Union. Retrieved 6 June 2019.
IAU 2006 resolution 3, see Recommendation and footnotes, note 3.
Fairhead, L. & Bretagnon, P. (1990) Astron. & Astrophys. 229, 240.
Kaplan, G. (2005), US Naval Observatory Circular 179.
https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html
https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems

Parameters: timescale The astronomical time scale in which the Julian Date is given ijd [day] integer part of the Julian day in the specified timescale fjd [day] fractional part Julian day value in the specified timescale leap [s] Leap seconds, e.g. as published by IERS Bulletin C. dut1 [s] UT1-UTC time difference, e.g. as published in IERS Bulletin A. [out] time Pointer to the data structure that uniquely defines the astronomical time for all applications.

Returns: 0 if successful, or else -1 if there was an error (errno will be set to indicate the type of error).

See also: novas_set_time(); novas_set_unix_time(); novas_get_split_time(); novas_timescale_for_string()

Since: 1.1

Author: Attila Kovacs

References NOVAS_GPS, NOVAS_TAI, NOVAS_TCB, NOVAS_TCG, NOVAS_TDB, NOVAS_TT, NOVAS_UT1, NOVAS_UTC, and tt2tdb().

◆ novas_set_time()

Sets an astronomical time to the fractional Julian Date value, defined in the specified timescale. The time set this way is accurate to a few μs (microseconds) due to the inherent precision of the double-precision argument. For higher precision applications you may use novas_set_split_time() instead, which has an inherent accuracy at the picosecond level.

Parameters: timescale The astronomical time scale in which the Julian Date is given jd [day] Julian day value in the specified timescale leap [s] Leap seconds, e.g. as published by IERS Bulletin C. dut1 [s] UT1-UTC time difference, e.g. as published in IERS Bulletin A. [out] time Pointer to the data structure that uniquely defines the astronomical time for all applications.

Returns: 0 if successful, or else -1 if there was an error (errno will be set to indicate the type of error).

See also: novas_set_split_time(); novas_set_unix_time(); novas_get_time(); novas_timescale_for_string()

Since: 1.1

Author: Attila Kovacs

References novas_set_split_time().

◆ novas_set_unix_time() int novas_set_unix_time ( time_t unix_time, long nanos, int leap, double dut1, novas_timespec *restrict time )

Sets an astronomical time to a UNIX time value. UNIX time is defined as UTC seconds measured since 0 UTC, 1 Jan 1970 (the start of the UNIX era). Specifying time this way supports precisions to the nanoseconds level by construct. Specifying UNIX time in split seconds and nanoseconds is a common way CLIB handles precision time, e.g. with struct timespec and functions like clock_gettime() (see time.h).

Parameters: unix_time [s] UNIX time (UTC) seconds nanos [ns] UTC sub-second component leap [s] Leap seconds, e.g. as published by IERS Bulletin C. dut1 [s] UT1-UTC time difference, e.g. as published in IERS Bulletin A. [out] time Pointer to the data structure that uniquely defines the astronomical time for all applications.

Returns: 0 if successful, or else -1 if there was an error (errno will be set to indicate the type of error).

See also: novas_set_time(); novas_get_unix_time(); clock_gettime(); struct timespec

Since: 1.1

Author: Attila Kovacs

References novas_set_split_time(), and NOVAS_UTC.

◆ novas_sets_below()

Returns the UTC date at which a distant source appears to set below the specified elevation angle. The calculated time will account for the (slow) motion of Solar-system bodies, and optionally for atmopsheric refraction also.

NOTES:

The current implementation is not suitable for calculating the nearest successive set times for near-Earth objects, at or within the geostationary orbit.
This function calculates the time when the center (not the limb!) of the source sets below the specified elevation threshold. Something to keep in mind for calculating Sun/Moon rise times.

Parameters: el [deg] Elevation angle. source Observed source frame Observing frame, defining the observer location and astronomical time of observation. ref_model Refraction model, or NULL to calculate unrefracted setting time.

Returns: [day] UTC-based Julian date at which the object sets below the specified elevation next after the specified date, or else NAN if the source stays above or below the given elevation for the entire 24-hour day..

Since: 1.3

Author: Attila Kovacs

See also: novas_rises_above(); novas_transit_time()

◆ novas_sky_pos()

Calculates an apparent location on sky for the source. The position takes into account the proper motion (for sidereal source), or is antedated for light-travel time (for Solar-System bodies). It also applies an appropriate aberration correction and gravitational deflection of the light.

To calculate corresponding local horizontal coordinates, you can pass the output RA/Dec coordinates to novas_app_to_hor(). Or to calculate apparent coordinates in other systems, you may pass the result to novas_transform_sy_pos() after.

And if you want geometric positions instead (not corrected for aberration or gravitational deflection), you may want to use novas_geom_posvel() instead.

The approximate 'inverse' of this function is novas_app_to_geom().

This function implements the same aberration and gravitational deflection corrections as place(), but at reduced computational cost. See place() for references. Unlike place(), however, the output always reports the distance calculated from the parallax for sidereal sources. Note also, that while place() does not apply aberration and gravitational deflection corrections when sys is NOVAS_ICRS (3), this routine will apply those corrections consistently for all coordinate systems (and you can use novas_geom_posvel() instead to get positions without aberration or deflection in any system).

NOTES:

If sys is NOVAS_TOD (true equator and equinox of date), the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C place() for that system. To obtain more precise TOD coordinates, set sys to NOVAS_CIRS here, and follow with cirs_to_tod() / cirs_to_app_ra() on the out->r_hat / out->ra respectively after (or you can use just convert one of the quantities, and use radec2vector() or vector2radec() to get the other even faster).
As of SuperNOVAS v1.3, the returned radial velocity component is a proper observer-based spectroscopic measure. In prior releases, and in NOVAS C 3.1, this was inconsistent, with LSR-based measures being returned for catalog sources.

Parameters: object Pointer to a celestial object data structure that is observed. Catalog sources should have coordinates and properties in ICRS. You can use transform_cat() to convert catalog entries to ICRS as necessary. frame The observer frame, defining the location and time of observation. sys The coordinate system in which to return the apparent sky location. [out] out Pointer to the data structure which is populated with the calculated apparent location in the designated coordinate system.

Returns: 0 if successful, 50–70 error is 50 + error from light_time2(), 70–80 error is 70 + error from grav_def(), or else -1 (errno will indicate the type of error).

See also: novas_geom_to_app(); novas_app_to_hor(); place(); cirs_to_tod(); cirs_to_app_ra()

Since: 1.1

Author: Attila Kovacs

References grav_planets(), NOVAS_CATALOG_OBJECT, NOVAS_FULL_ACCURACY, novas_geom_posvel(), novas_geom_to_app(), NOVAS_ICRS, NOVAS_REDUCED_ACCURACY, novas_vlen(), rad_vel2(), and object::type.

◆ novas_ssb_to_lsr_vel() double novas_ssb_to_lsr_vel ( double epoch, double ra, double dec, double vLSR )

Returns a radial-velocity referenced to the Local Standard of Rest (LSR) for a given Solar-System Barycentric (SSB) radial velocity. Internally, NOVAS always uses barycentric radial velocities, but it is just as common to have catalogs define radial velocities referenced to the LSR.

The SSB motion w.r.t. the barycenter is assumed to be (11.1, 12.24, 7.25) km/s in ICRS (Shoenrich et al. 2010).

REFERENCES:

Ralph Schoenrich, James Binney, Walter Dehnen, Monthly Notices of the Royal Astronomical Society, Volume 403, Issue 4, April 2010, Pages 1829–1833, https://doi.org/10.1111/j.1365-2966.2010.16253.x

Parameters: epoch [yr] Coordinate epoch in which the coordinates and velocities are defined. E.g. 2000.0. ra [h] Right-ascenscion of source at given epoch. dec [deg] Declination of source at given epoch. vLSR [km/s] radial velocity defined against the Local Standard of Rest (LSR), at given epoch.

Returns: [km/s] Equivalent Solar-System Barycentric radial velocity.

Since: 1.3

Author: Attila Kovacs

See also: make_cat_entry(); novas_lsr_to_ssb_vel()

References NOVAS_JD_J2000, precession(), and radec2vector().

◆ novas_standard_refraction()

Returns an optical refraction correction for a standard atmosphere.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian data of observation (unused in this implementation of RefractionModel) loc Pointer to structure defining the observer's location on earth, and local weather type Whether the input elevation is observed or astrometric: NOVAS_REFRACT_OBSERVED (-1) or NOVAS_REFRACT_ASTROMETRIC (0). el [deg] Astrometric (unrefracted) source elevation

Returns: [deg] Estimated refraction, or NAN if there was an error (it should also set errno to indicate the type of error).

See also: novas_app_to_hor(); novas_optical_refraction(); NOVAS_STANDARD_ATMOSPHERE(); refract(); refract_astro()

References NOVAS_STANDARD_ATMOSPHERE.

◆ novas_str_degrees() double novas_str_degrees ( const char *restrict str )

Returns an angle parsed from a string that contains either a decimal degrees or else a broken-down DMS representation. See novas_parse_degrees() to see what string representations may be used.

To see if the string was fully parsed when returning a valid (non-NAN) value, you can check errno: it should be zero (0) if all non-whitespace and punctuation characters have been parsed from the input string, or else EINVAL if the parsed value used only the leading part of the string.

Parameters: str The input string that specified an angle either as decimal degrees or as a broken down DMS speficication. The decimal value may be immediately followed by a letter 'd'. See more in novas_parse_degrees() on acceptable input specifications.

Returns: [deg] The angle represented by the string, or else NAN if the string could not be parsed into an angle value (errno will indicate the type of error).

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_degrees(); novas_parse_dms(); novas_print_dms(); novas_str_hours()

References novas_parse_degrees().

◆ novas_str_hours() double novas_str_hours ( const char *restrict str )

Returns a time or time-like angleparsed from a string that contains either a decimal hours or else a broken-down HMS representation. See novas_parse_hours() to see what string representations may be used.

To check if the string was fully parsed when returning a valid (non-NAN) value you can check errno: it should be zero (0) if all non-whitespace and punctuation characters have been parsed from the input string, or else EINVAL if the parsed value used only the leading part of the string.

Parameters: str The input string that specified an angle either as decimal hours or as a broken down HMS speficication. The decimal value may be immediately followed by a letter 'h'. See more in novas_parse_hours() on acceptable input specifications.

Returns: [h] The time-like value represented by the string, or else NAN if the string could not be parsed into a time-like value (errno will indicate the type of error).

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_hours(); novas_parse_hms(); novas_print_hms(); novas_str_degrees()

References novas_parse_hours().

◆ novas_time_gst() ◆ novas_time_lst()

Returns the Local (apparent) Sidereal Time (LST/LaST) for a given astronomical time specification and observer location.

Parameters: time The astronomoical time specification. lon [deg] The geodetic longitude of the observer. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1).

Returns: [h] The Local apparent Sidereal Time (LST / LaST) in the [0:24) hour range, or else NAN if there was an error (errno will indicate the type of error).

Since: 1.4

Author: Attila Kovacs

See also: novas_frame_lst(); novas_set_time()

References novas_time_gst().

◆ novas_timescale_for_string() enum novas_timescale novas_timescale_for_string ( const char *restrict str )

Returns the timescale constant for a string that denotes the timescale in with a standard abbreviation (case insensitive). The following values are recognised: "UTC", "UT", "UT0", "UT1", "GMT", "TAI", "GPS", "TT", "ET", "TCG", "TCB", "TDB".

Parameters: str String specifying an astronomical timescale

Returns: The SuperNOVAS timescale constant (<=0), or else -1 if the string was NULL, empty, or could not be matched to a timescale value (errno will be set to EINVAL also).

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_timescale(); novas_set_time(); novas_set_split_time(); novas_print_timescale()

References NOVAS_GPS, NOVAS_TAI, NOVAS_TCB, NOVAS_TCG, NOVAS_TDB, NOVAS_TT, NOVAS_UT1, and NOVAS_UTC.

◆ novas_timestamp()

Prints an astronomical timestamp to millisecond precision in the specified timescale to the specified string buffer. It differs from ISO 8601 timestamps for dates prior to the Gregorian calendar reform of 1582 October 15 (otherwise two are identical). E.g.:

 2025-01-26T21:32:49.701 TAI

NOTES:

The timestamp uses the astronomical date. That is Gregorian dates after the Gregorian calendar reform of 15 October 1582, and Julian/Roman dates prior to that. This is in contrast to ISO 8601 timestamps, which use Gregorian dates even for dates the precede the calendar reform that introduced them.
B.C. dates are indicated with years <=0 according to the astronomical and ISO 8601 convention, i.e., X B.C. as (1-X), so 45 B.C. as -44.

Parameters: time Pointer to the astronomical time specification data structure. scale The timescale to use. [out] dst Output string buffer. At least 28 bytes are required for a complete timestamp with termination. maxlen The maximum number of characters that can be printed into the output buffer, including the string termination. If the full ISO timestamp is longer than maxlen, then it will be truncated to fit in the allotted space, including a termination character.

Returns: the number of characters printed into the string buffer, not including the termination. As such it is at most maxlen - 1.

Since: 1.3

Author: Attila Kovacs

See also: novas_iso_timestamp(); novas_parse_date()

References NOVAS_ASTRONOMICAL_CALENDAR, novas_get_split_time(), and novas_print_timescale().

◆ novas_track_pos() int novas_track_pos ( const novas_track * track, const novas_timespec * time, double *restrict lon, double *restrict lat, double *restrict dist, double *restrict z )

Calculates a projected position and redshift for a source, given the available tracking position and derivatives. Using 'tracks' to project positions can be much faster than the repeated full recalculation of the source position over some short period.

In SuperNOVAS terminology a 'track' is a 2nd order Taylor series expansion of the observed position and redshift in time. For most but the fastest moving sources, horizontal (Az/El) tracks are sufficiently precise on minute timescales, whereas depending on the type of source equatorial tracks can be precise for up to days.

Parameters: track Tracking position and motion (first and second derivatives) time Astrometric time of observation [out] lon [deg] projected observed Eastward longitude in tracking coordinate system [out] lat [deg] projected observed latitude in tracking coordinate system [out] dist [AU] projected apparent distance to source from observer [out] z projected observed redshift

Returns: 0 if successful, or else -1 if either input pointer is NULL (errno is set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_equ_track(); novas_hor_track(); novas_z2v()

References novas_track::accel, novas_observable::dist, novas_observable::lat, novas_observable::lon, novas_diff_time(), novas_track::pos, novas_track::rate, novas_track::time, and novas_observable::z.

◆ novas_transform_sky_pos()

Transforms a position or velocity 3-vector from one coordinate reference system to another.

Parameters: in Input apparent position on sky in the original coordinate reference system transform Pointer to a coordinate transformation matrix [out] out Output apparent position on sky in the new coordinate reference system. It may be the same as the input.

Returns: 0 if successful, or else -1 if there was an error (errno will indicate the type of error).

See also: novas_make_transform(); novas_transform_vector()

Since: 1.1

Author: Attila Kovacs

References sky_pos::dec, sky_pos::r_hat, sky_pos::ra, and vector2radec().

◆ novas_transform_vector() int novas_transform_vector ( const double * in, const novas_transform *restrict transform, double * out )

Transforms a position or velocity 3-vector from one coordinate reference system to another.

Parameters: in Input 3-vector in the original coordinate reference system transform Pointer to a coordinate transformation matrix [out] out Output 3-vector in the new coordinate reference system. It may be the same as the input.

Returns: 0 if successful, or else -1 if there was an error (errno will indicate the type of error).

See also: novas_make_transform(); novas_transform_skypos()

Since: 1.1

Author: Attila Kovacs

◆ novas_transit_time() double novas_transit_time ( const object *restrict source, const novas_frame *restrict frame )

Returns the UTC date at which a source transits the local meridian. The calculated time will account for the (slow) motion of Solar-system bodies.

NOTES:

The current implementation is not suitable for calculating the nearest successive transit times for near-Earth objects, at or within the geostationary orbit.

Parameters: source Observed source frame Observing frame, defining the observer location and astronomical time of observation.

Returns: [day] UTC-based Julian date at which the object transits the local meridian next after the specified date, or NAN if either input pointer is NULL.

Since: 1.3

Author: Attila Kovacs

See also: novas_rises_above(); novas_sets_below()

◆ novas_uvw_to_xyz() int novas_uvw_to_xyz ( const double * uvw, double ha, double dec, double * xyz )

Converts equatorial u,v,w projected (absolute or relative) coordinates to rectangular telescope x,y,z coordinates (in ITRS) to for a specified line of sight.

u,v,w are Cartesian coordinates (u,v) along the local equatorial R.A. and declination directions as seen from a direction on the sky (w). As such, they are effectively ITRS-based line-of-sight (LOS) coordinates.

x,y,z are Cartesian coordinates w.r.t the Greenwich meridian in the ITRS frame. The directions are x: long=0, lat=0; y: long=90, lat=0; z: lat=90.

Parameters: xyz [arb.u.] Absolute or relative u,v,w coordinates (double[3]). ha [h] Hourangle (LST - RA) i.e., the difference between the Local (apparent) Sidereal Time and the apparent (true-of-date) Right Ascension of observed source. dec [deg] Apparent (true-of-date) declination of source [out] uvw [arb.u.] Converted x,y,z coordinates (double[3]) in the same unit as uvw. It may be the same vector as the input.

Returns: 0 if successful, or else -1 if either vector argument is NULL (errno will be set to EINVAL)

Since: 1.3

Author: Attila Kovacs

See also: novas_xyz_to_uvw()

References novas_los_to_xyz().

◆ novas_v2z() double novas_v2z ( double vel )

Converts a radial recession velocity to a redshift value (z = δf / f_rest). It is based on the relativistic formula:

 1 + z = sqrt((1 + β) / (1 - β))

where β = v / c.

Parameters: vel [km/s] velocity (i.e. rate) of recession.

Returns: the corresponding redshift value (δλ / λ_rest), or NAN if the input velocity is invalid (i.e., it exceeds the speed of light).

See also: novas_z2v(); novas_z_add()

Author: Attila Kovacs

Since: 1.2

References NOVAS_KMS.

◆ novas_wave_refraction()

The wavelength-dependent IAU atmospheric refraction model, based on the SOFA iauRefco() function, in compliance to the 'SOFA Software License' terms of the original source. Our implementation is not provided nor it is endorsed by SOFA. The original function has been modified slightly, such as:

Out-of-range weather parameters will return with an error (errno set to EINVAL), unlike the SOFA implementation, which sets minimal or maximal allowed values for these.
The algorithm has been simplified to use fewer variables and simpler logic.
The SOFA function this implementation is based on returns A/B coefficients, whereas this implementation returns the refraction correction angle.

The refraction is calculated for the observing wavelenth previously set via novas_refract_wavelength(), or for visible light at 550 nm by default.

The function uses the weather parameters defined for the location, including humidity. As such, make sure the weather data is fully defined, and that the humidity was explicitly set after calling make_on_surface().

According to the documentation of SOFA's iauRefco() function, the model has the following accuracy for elevation angles between 15 and 75 degrees, under a range of typical surface conditions:

worst RMS optical/IR 62 mas 8 mas radio 319 mas 49 mas

NOTES:

From the SOFA documentation: "The model balances speed and accuracy to give good results in applications where performance at low altitudes is not paramount. Performance is maintained across a range of conditions, and applies to both optical/IR and radio."
The model is divergent in the observed direction of the horizon. As such, it should not be used for calculating refraction at or below the horizon itself.

REFERENCES:

Crane, R.K., Meeks, M.L. (ed), "Refraction Effects in the Neutral Atmosphere", Methods of Experimental Physics: Astrophysics 12B, Academic Press, 1976.
Gill, Adrian E., "Atmosphere-Ocean Dynamics", Academic Press, 1982.
Green, R.M., "Spherical Astronomy", Cambridge University Press, 1987.
Hohenkerk, C.Y., & Sinclair, A.T., NAO Technical Note No. 63, 1985.
Rueger, J.M., "Refractive Index Formulae for Electronic Distance Measurement with Radio and Millimetre Waves", in Unisurv Report S-68, School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia, 2002.
Stone, Ronald C., P.A.S.P. 108, 1051-1058, 1996.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian data of observation (unused in this implementation of RefractionModel) loc Pointer to structure defining the observer's location on earth, and local weather. Make sure all weather values, including humidity (added in v1.1), are fully populated. type Whether the input elevation is observed or astrometric: NOVAS_REFRACT_OBSERVED (-1) or NOVAS_REFRACT_ASTROMETRIC (0). el [deg] observed source elevation of the specified type.

Returns: [deg] Estimated refraction, or NAN if there was an error (it should also set errno to indicate the type of error), e.g. because the location is NULL, or because the weather parameters are outside of the supported (sensible) range, or because the elevation is outside of the supported (0:90] range, or because the wavelength set is below 100 nm (0.1 μm);

Since: 1.4

Author: Attila Kovacs

See also: novas_refract_wavelength(); novas_optical_refraction(); novas_radio_refraction(); make_on_surface(); on_surface

References on_surface::humidity, novas_inv_refract(), NOVAS_REFRACT_ASTROMETRIC, NOVAS_REFRACT_OBSERVED, novas_wave_refraction(), on_surface::pressure, and on_surface::temperature.

◆ novas_xyz_to_los() int novas_xyz_to_los ( const double * xyz, double lon, double lat, double * los )

Converts a 3D rectangular equatorial (δx, δy, δz) vector to a polar (δφ, δθ δr) vector along a line-of-sight.

Parameters: xyz [arb.u.] Rectangular equatorial 3-vector (δx, δy, δz). lon [deg] Line-of-sight longitude. lat [deg] Line-of-sight latitude. [out] los [arb.u.] Output line-of-sight 3-vector (δφ, δθ δr), in the same units as the input. It may be the same vector as the input.

Returns: 0 if successful, or else -1 if either vector argument is NULL (errno will be set to EINVAL).

Since: 1.3

Author: Attila Kovacs

See also: novas_los_to_xyz(); novas_xyz_to_uvw()

◆ novas_xyz_to_uvw() int novas_xyz_to_uvw ( const double * xyz, double ha, double dec, double * uvw )

Converts rectangular telescope x,y,z (absolute or relative) coordinates (in ITRS) to equatorial u,v,w projected coordinates for a specified line of sight.

x,y,z are Cartesian coordinates w.r.t the Greenwich meridian, in the ITRS frame. The directions are x: long=0, lat=0; y: long=90, lat=0; z: lat=90.

Parameters: xyz [arb.u.] Absolute or relative x,y,z coordinates (double[3]). ha [h] Hourangle (LST - RA) i.e., the difference between the Local (apparent) Sidereal Time and the apparent (true-of-date) Right Ascension of observed source. dec [deg] Apparent (true-of-date) declination of source [out] uvw [arb.u.] Converted u,v,w coordinates (double[3]) in same units as xyz. It may be the same vector as the input.

Returns: 0 if successful, or else -1 if either vector argument is NULL (errno will be set to EINVAL)

Since: 1.3

Author: Attila Kovacs

See also: novas_uvw_to_xyz()

References novas_xyz_to_los().

◆ novas_z2v() double novas_z2v ( double z )

==========================================================================

Converts a redshift value (z = δf / f_rest) to a radial velocity (i.e. rate) of recession. It is based on the relativistic formula:

 1 + z = sqrt((1 + β) / (1 - β))

where β = v / c.

Parameters: z the redshift value (δλ / λ_rest).

Returns: [km/s] Corresponding velocity of recession, or NAN if the input redshift is invalid, i.e. z <= -1).

See also: novas_v2z(); redshift_vrad()

Author: Attila Kovacs

Since: 1.2

References NOVAS_KMS.

◆ novas_z_add() double novas_z_add ( double z1, double z2 )

Compounds two redshift corrections, e.g. to apply (or undo) a series gravitational redshift corrections and/or corrections for a moving observer. It's effectively using (1 + z) = (1 + z1) * (1 + z2).

Parameters: z1 One of the redshift values z2 The other redshift value

Returns: The compound redshift value, ot NAN if either input redshift is invalid (errno will be set to EINVAL).

See also: grav_redshift(); redshift_vrad(); unredshift_vrad()

Since: 1.2

Author: Attila Kovacs

◆ novas_z_inv() double novas_z_inv ( double z )

Returns the inverse of a redshift value, that is the redshift for a body moving with the same velocity as the original but in the opposite direction.

Parameters

Returns: The redshift value for a body moving in the opposite direction with the same speed, or NAN if the input redshift is invalid.

See also: novas_z_add()

Since: 1.2

Author: Attila Kovacs

◆ nutation()

Nutates equatorial rectangular coordinates from mean equator and equinox of epoch to true equator and equinox of epoch. Inverse transformation may be applied by setting flag 'direction'.

This is the old (pre IAU 2006) method of nutation calculation. If you follow the now standard IAU 2000/2006 methodology you will want to use nutation_angles() instead.

REFERENCES:

Explanatory Supplement To The Astronomical Almanac, pp. 114-115.

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date direction NUTATE_MEAN_TO_TRUE (0) or NUTATE_TRUE_TO_MEAN (-1; or non-zero) accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in Position 3-vector, geocentric equatorial rectangular coordinates, referred to mean equator and equinox of epoch. [out] out Position vector, geocentric equatorial rectangular coordinates, referred to true equator and equinox of epoch. It can be the same as the input position.

Returns: 0 if successful, or -1 if one of the vector arguments is NULL.

See also: nutation_angles(); tt2tdb(); NOVAS_TOD

References e_tilt(), and NUTATE_MEAN_TO_TRUE.

◆ nutation_angles() int nutation_angles ( double t, enum novas_accuracy accuracy, double *restrict dpsi, double *restrict deps )

Returns the values for nutation in longitude and nutation in obliquity for a given TDB Julian date. The nutation model selected depends upon the input value of 'accuracy'. See notes below for important details.

This function selects the nutation model depending first upon the input value of 'accuracy'. If 'accuracy' is NOVAS_FULL_ACCURACY (0), the IAU 2000A nutation model is used. Otherwise the model set by set_nutation_lp_provider() is used, or else the default nu2000k().

See the prologs of the nutation functions in file 'nutation.c' for details concerning the models.

NOTES:

As of version 1.4, this function applies the recommended rescaling of the IAU 2000 nutation angles by the factors recommended by the P03rev2 (Capitaine et al. 2005; Coppola et al. 2009), to match the model used by SOFA.

REFERENCES:

Kaplan, G. (2005), US Naval Observatory Circular 179.
Capitaine, N., P.T. Wallace and J. Chapront (2005), “Improvement of the IAU 2000 precession model.” Astronomy & Astrophysics, Vol. 432, pp. 355–67.
Coppola, V., Seago, G.H., & Vallado, D.A. (2009), AAS 09-159

Parameters: t [cy] TDB time in Julian centuries since J2000.0 accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] dpsi [arcsec] Nutation in longitude in arcseconds. [out] deps [arcsec] Nutation in obliquity in arcseconds.

Returns: 0 if successful, or -1 if the output pointer arguments are NULL

See also: set_nutation_lp_provider(); nutation(); iau2000b(); nu2000k(); cio_basis(); NOVAS_CIRS; NOVAS_JD_J2000

References get_nutation_lp_provider(), iau2000a(), and NOVAS_FULL_ACCURACY.

◆ obs_planets()

Calculates the positions and velocities for the Solar-system bodies, e.g. for use for graviational deflection calculations. The planet positions are calculated relative to the observer location, while velocities are w.r.t. the SSB. Both positions and velocities are antedated for light travel time, so they accurately reflect the apparent position (and barycentric motion) of the bodies from the observer's perspective.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1). In full accuracy mode, it will calculate the deflection due to the Sun, Jupiter, Saturn and Earth. In reduced accuracy mode, only the deflection due to the Sun is calculated. pos_obs [AU] Position 3-vector of observer (or the geocenter), with respect to origin at solar system barycenter, referred to ICRS axes, components in AU. pl_mask Bitwise (1 << planet-number) mask indicating which planets to request data for. See enum novas_planet for the enumeration of planet numbers. [out] planets Pointer to apparent planet data to populate. have positions and velocities calculated successfully. See enum novas_planet for the enumeration of planet numbers.

Returns: 0 if successful, -1 if any of the pointer arguments is NULL or if the output vector is the same as pos_obs, or the error from ephemeris().

See also: enum novas_planet; grav_planets(); grav_undo_planets(); set_planet_provider(); set_planet_provider_hp()

Since: 1.1

Author: Attila Kovacs

References light_time2(), make_planet(), novas_debug(), NOVAS_DEBUG_EXTRA, NOVAS_DEBUG_OFF, novas_get_debug_mode(), NOVAS_PLANETS, and NOVAS_SUN.

◆ obs_posvel() int obs_posvel ( double jd_tdb, double ut1_to_tt, enum novas_accuracy accuracy, const observer *restrict obs, const double *restrict geo_pos, const double *restrict geo_vel, double *restrict pos, double *restrict vel )

Calculates the ICRS position and velocity of the observer relative to the Solar System Barycenter (SSB).

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date. ut1_to_tt [s] TT - UT1 time difference. Used only when 'location->where' is NOVAS_OBSERVER_ON_EARTH (1) or NOVAS_OBSERVER_IN_EARTH_ORBIT (2). accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) obs The observer location, relative to which the output positions and velocities are to be calculated geo_pos [AU] ICRS position vector of the geocenter w.r.t. the Solar System Barycenter (SSB). If either geo_pos or geo_vel is NULL, it will be calculated when needed. geo_vel [AU/day] ICRS velocity vector of the geocenter w.r.t. the Solar System Barycenter (SSB). If either geo_pos or geo_vel is NULL, it will be calculated when needed. [out] pos [AU] Position 3-vector of the observer w.r.t. the Solar System Barycenter (SSB). It may be NULL if not required. [out] vel [AU/day] Velocity 3-vector of the observer w.r.t. the Solar System Barycenter (SSB). It must be distinct from the pos output vector, and may be NULL if not required.

Returns: 0 if successful, or the error from geo_posvel(), or else -1 (with errno indicating the type of error).

Author: Attila Kovacs

Since: 1.3

See also: place()

References ephemeris(), geo_posvel(), NOVAS_AIRBORNE_OBSERVER, NOVAS_BARYCENTER, NOVAS_EARTH_INIT, NOVAS_OBSERVER_IN_EARTH_ORBIT, NOVAS_OBSERVER_ON_EARTH, NOVAS_OBSERVER_PLACES, NOVAS_SOLAR_SYSTEM_OBSERVER, and tt2tdb().

◆ place()

Computes the apparent direction of a celestial object at a specified time and in a specified coordinate system and a specific near-Earth origin.

While coord_sys defines the celestial pole (i.e. equator) orientation of the coordinate system, location->where sets the origin of the reference place relative to which positions and velocities are reported.

For all but ICRS coordinate outputs, the calculated positions and velocities include aberration corrections for the moving frame of the observer as well as gravitational deflection due to the Sun and Earth and other major gravitating bodies in the Solar system, provided planet positions are available via a novas_planet_provider function.

In case of a dynamical equatorial system (such as CIRS or TOD) and an Earth-based observer, the polar wobble parameters set via a prior call to cel_pole() together with he ut1_to_tt argument decide whether the resulting 'topocentric' output frame is Pseudo Earth Fixed (PEF; if cel_pole() was not set and DUT1 is 0) or ITRS (actual rotating Earth; if cel_pole() was set and ut1_to_tt includes the DUT1 component).

NOTES:

This version fixes a NOVAS C 3.1 issue that velocities and solar-system distances were not antedated for light-travel time.
In a departure from the original NOVAS C, the radial velocity for major planets (and Sun and Moon) includes gravitational redshift corrections for light originating at the surface, assuming it's observed from near Earth or else from a large distance away.
If sys is NOVAS_TOD (true equator and equinox of date), the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C place() for that system. To obtain more precise TOD coordinates, set sys to NOVAS_CIRS here, and follow with cirs_to_tod() after.
As of SuperNOVAS v1.3, the returned radial velocity component is a proper observer-based spectroscopic measure. In prior releases, and in NOVAS C 3.1, this was inconsistent, with pseudo LSR-based measures being returned for catalog sources.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Klioner, S. (2003), Astronomical Journal 125, 1580-1597.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. source Pointer to a celestrial object data structure. Catalog objects musy have ICRS coordinates. You can use transform_cat() to convert other catalog systems to ICRS as necessary. location The observer location, relative to which the output positions and velocities are to be calculated ut1_to_tt [s] TT - UT1 time difference. Used only when 'location->where' is NOVAS_OBSERVER_ON_EARTH (1) or NOVAS_OBSERVER_IN_EARTH_ORBIT (2). coord_sys The coordinate system that defines the orientation of the celestial pole. If it is NOVAS_ICRS (3), a geometric position and radial velocity is returned. For all other systems, the returned position is the apparent position including aberration and gravitational deflection corrections, and the radial velocity is in the direction the eflected light was emitted from the source. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] output Data structure to populate with the result.

Returns: 0 if successful,
1 if 'coord_sys' is invalid,
2 if 'accuracy' is invalid,
3 if the observer is at or very near (within ~1.5m of) the observed location,
10–40: error is 10 + the error ephemeris(),
40–50: error is 40 + the error from geo_posvel(),
50–70: error is 50 + error from light_time2(),
70–80: error is 70 + error from grav_def(),
80–90: error is 80 + error from cio_location(),
90–100: error is 90 + error from cio_basis().

See also: novas_geom_posvel(); novas_sky_pos(); place_star(); place_icrs(); place_gcrs(); place_cirs(); radec_star(); radec_planet(); cel_pole(); get_ut1_to_tt()

References aberration(), bary2obs(), d_light(), ephemeris(), era(), gcrs_to_cirs(), gcrs_to_j2000(), gcrs_to_mod(), gcrs_to_tod(), grav_bodies_full_accuracy, grav_bodies_reduced_accuracy, grav_planets(), light_time2(), make_observer_at_geocenter(), NOVAS_BARYCENTER, NOVAS_CATALOG_OBJECT, NOVAS_CIRS, NOVAS_EARTH_INIT, NOVAS_FULL_ACCURACY, NOVAS_ICRS, NOVAS_ITRS, NOVAS_J2000, NOVAS_MOD, NOVAS_REDUCED_ACCURACY, NOVAS_SUN_INIT, NOVAS_TIRS, NOVAS_TOD, novas_vlen(), obs_planets(), obs_posvel(), proper_motion(), rad_vel2(), spin(), starvectors(), tt2tdb(), and vector2radec().

◆ place_cirs()

Computes the Celestial Intermediate Reference System (CIRS) dynamical position position of a source as 'seen' from the geocenter at the given time of observation. See place() for more information.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date of observation. source Catalog source or solar_system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos Structure to populate with the calculated CIRS position data

Returns: 0 if successful, or -1 if any of the input pointer arguments is NULL, or else an error from place().

See also: place_tod(); place_gcrs()

Since: 1.0

Author: Attila Kovacs

References NOVAS_CIRS, and place().

◆ place_gcrs()

Computes the Geocentric Celestial Reference System (GCRS) position of a source (as 'seen' from the geocenter) at the given time of observation. Unlike place_icrs(), this includes aberration for the moving frame of the geocenter as well as gravitational deflections calculated for a virtual observer located at the geocenter. See place() for more information.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date of observation. source Catalog source or solar_system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos Structure to populate with the calculated GCRS position data

Returns: 0 if successful, or -1 if any of the input pointer arguments is NULL, or else an error from place().

See also: place_icrs(); place_cirs(); place_tod(); virtual_star(); virtual_planet()

Since: 1.0

Author: Attila Kovacs

References NOVAS_GCRS, and place().

◆ place_icrs()

Computes the International Celestial Reference System (ICRS) position of a source. (from the geocenter). Unlike place_gcrs(), this version does not include aberration or gravitational deflection corrections.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date of observation. source Catalog source or solar_system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos Structure to populate with the calculated geocentric ICRS position data (Unlike place_gcrs(), the calculated coordinates do not account for aberration or gravitational deflection).

Returns: 0 if successful, or -1 if any of the input pointer arguments is NULL, or else an error from place().

See also: place_gcrs(); place_cirs(); place_tod(); mean_star()

Since: 1.0

Author: Attila Kovacs

References NOVAS_ICRS, and place().

◆ place_j2000()

Computes the J2000 dynamical position position of a source as 'seen' from the geocenter at the given time of observation. See place() for more information.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date of observation. source Catalog source or solar_system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos Structure to populate with the calculated CIRS position data

Returns: 0 if successful, or -1 if any of the input pointer arguments is NULL, or else an error from place().

See also: place_cirs(); place_gcrs(); app_star(); app_planet()

Since: 1.1

Author: Attila Kovacs

References NOVAS_J2000, and place().

◆ place_mod()

Computes the Mean of Date (MOD) dynamical position position of a source as 'seen' from the geocenter at the given time of observation. See place() for more information.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date of observation. source Catalog source or solar_system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos Structure to populate with the calculated CIRS position data

Returns: 0 if successful, or -1 if any of the input pointer arguments is NULL, or else an error from place().

See also: place_cirs(); place_gcrs(); app_star(); app_planet()

Since: 1.1

Author: Attila Kovacs

References NOVAS_MOD, and place().

◆ place_star()

Computes the apparent place of a star, referenced to dynamical equator at date 'jd_tt', given its catalog mean place, proper motion, parallax, and radial velocity. See place() for more information.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. obs Observer location (NULL defaults to geocentric) ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. system The type of coordinate reference system in which coordinates are to be returned. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos The position and radial velocity of of the catalog source in the specified coordinate system and relative to the specified observer location (if applicable)

Returns: 0 if successful, or -1 if one of the required arguments is NULL, or else 1 if the observer location is invalid, or an error code from place().

See also: get_ut1_to_tt()

Author: Attila Kovacs

Since: 1.0

References NOVAS_CATALOG_OBJECT, place(), object::star, and object::type.

◆ place_tod()

Computes the True of Date (TOD) dynamical position position of a source as 'seen' from the geocenter at the given time of observation. See place() for more information.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date of observation. source Catalog source or solar_system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] pos Structure to populate with the calculated CIRS position data

Returns: 0 if successful, or -1 if any of the input pointer arguments is NULL, or else an error from place().

See also: place_cirs(); place_gcrs(); app_star(); app_planet()

Since: 1.0

Author: Attila Kovacs

References NOVAS_TOD, and place().

◆ planet_lon()

Returns the planetary longitude, for Mercury through Neptune, w.r.t. mean dynamical ecliptic and equinox of J2000, with high order terms omitted (Simon et al. 1994, 5.8.1-5.8.8).

Parameters: t [cy] Julian centuries since J2000 planet Novas planet id, e.g. NOVAS_MARS.

Returns: [rad] The approximate longitude of the planet in radians [-π:π], or NAN if the planet id is out of range.

See also: accum_prec(); nutation_angles(); ee_ct(); NOVAS_JD_J2000

Since: 1.0

Author: Attila Kovacs

References NOVAS_NEPTUNE, and TWOPI.

◆ precession() short precession ( double jd_tdb_in, const double * in, double jd_tdb_out, double * out )

Precesses equatorial rectangular coordinates from one epoch to another. Unlike the original NOVAS routine, this routine works for any pairing of the time arguments.

This function calculates precession for the old (pre IAU 2000) methodology. Its main use for NOVAS users is to allow converting older catalog coordinates e.g. to J2000 coordinates, which then can be converted to the now standard ICRS system via frame_tie().

NOTE:

Unlike the original NOVAS C 3.1 version, this one does not require that one of the time arguments must be J2000. You can precess from any date to any other date, and the intermediate epoch of J2000 will be handled internally as needed.
This function caches the results of the last calculation in case it may be re-used at no extra computational cost for the next call.

REFERENCES:

Explanatory Supplement To The Astronomical Almanac, pp. 103-104.
Capitaine, N. et al. (2003), Astronomy And Astrophysics 412, pp. 567-586.
Hilton, J. L. et al. (2006), IAU WG report, Celest. Mech., 94, pp. 351-367.
Capitaine, N., P.T. Wallace and J. Chapront (2005), “Improvement of the IAU 2000 precession model.” Astronomy & Astrophysics, Vol. 432, pp. 355–67.
Liu, J.-C., &amp Capitaine, N. (2017), A&A 597, A83

Parameters: jd_tdb_in [day] Barycentric Dynamic Time (TDB) based Julian date of the input epoch in Position 3-vector, geocentric equatorial rectangular coordinates, referred to mean dynamical equator and equinox of the initial epoch. jd_tdb_out [day] Barycentric Dynamic Time (TDB) based Julian date of the output epoch [out] out Position 3-vector, geocentric equatorial rectangular coordinates, referred to mean dynamical equator and equinox of the final epoch. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the position vectors is NULL.

See also: nutation(); frame_tie(); novas_epoch(); tt2tdb(); cio_basis(); NOVAS_TOD; NOVAS_JD_J2000; NOVAS_JD_B1950; NOVAS_JD_B1900

References precession().

◆ proper_motion() int proper_motion ( double jd_tdb_in, const double * pos, const double *restrict vel, double jd_tdb_out, double * out )

Applies proper motion, including foreshortening effects, to a star's position.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: jd_tdb_in [day] Barycentric Dynamical Time (TDB) based Julian date of the first epoch. pos [AU] Position vector at first epoch. vel [AU/day] Velocity vector at first epoch. jd_tdb_out [day] Barycentric Dynamical Time (TDB) based Julian date of the second epoch. [out] out Position vector at second epoch. It can be the same vector as the input.

Returns: 0 if successful, or -1 if any of the vector areguments is NULL.

See also: transform_cat()

◆ rad_vel() int rad_vel ( const object *restrict source, const double *restrict pos_src, const double * vel_src, const double * vel_obs, double d_obs_geo, double d_obs_sun, double d_src_sun, double *restrict rv )

Predicts the radial velocity of the observed object as it would be measured by spectroscopic means. Radial velocity is here defined as the radial velocity measure (z) times the speed of light. For major planets (and Sun and Moon), it includes gravitational corrections for light originating at the surface and observed from near Earth or else from a large distance away. For other solar system bodies, it applies to a fictitious emitter at the center of the observed object, assumed massless (no gravitational red shift). The corrections do not in general apply to reflected light. For stars, it includes all effects, such as gravitational redshift, contained in the catalog barycentric radial velocity measure, a scalar derived from spectroscopy. Nearby stars with a known kinematic velocity vector (obtained independently of spectroscopy) can be treated like solar system objects.

Gravitational blueshift corrections for the Solar and Earth potential for observers are included. However, the result does not include a blueshift correction for observers (e.g. spacecraft) orbiting other major Solar-system bodies. You may adjust the amount of gravitational redshift correction applied to the radial velocity via redshift_vrad(), unredshift_vrad() and grav_redshift() if necessary.

All the input arguments are BCRS quantities, expressed with respect to the ICRS axes. 'vel_src' and 'vel_obs' are kinematic velocities - derived from geometry or dynamics, not spectroscopy.

If the object is outside the solar system, the algorithm used will be consistent with the IAU definition of stellar radial velocity, specifically, the barycentric radial velocity measure, which is derived from spectroscopy. In that case, the vector 'vel_src' can be very approximate – or, for distant stars or galaxies, zero – as it will be used only for a small geometric correction that is proportional to proper motion.

Any of the distances (last three input arguments) can be set to zero (0.0) or negative if the corresponding general relativistic gravitational potential term is not to be evaluated. These terms generally are important at the meter/second level only. If 'd_obs_geo' and 'd_obs_sun' are both zero, an average value will be used for the relativistic term for the observer, appropriate for an observer on the surface of the Earth. 'd_src_sun', if given, is used only for solar system objects.

NOTES:

This function does not accont for the gravitational deflection of Solar-system sources. For that purpose, the rad_vel2() function, introduced in v1.1, is more appropriate.
The NOVAS C implementation did not include relatistic corrections for a moving observer if both d_obs_geo and d_obs_sun were zero. As of SuperNOVAS v1.1, the relatistic corrections for a moving observer will be included in the radial velocity measure always.
In a departure from the original NOVAS C, the radial velocity for major planets (and Sun and Moon) includes gravitational redshift corrections for light originating at the surface, assuming it's observed from near Earth or else from a large distance away.

REFERENCES:

Lindegren & Dravins (2003), Astronomy & Astrophysics 401, 1185-1201.
Unlike NOVAS C, this function will return a radial velocity for the Sun that is gravitationally referenced to the Sun's photosphere. (NOVAS C returns the radial velocity for a massless Sun)

Parameters: source Celestial object observed pos_src [AU|*] Geometric position vector of object with respect to observer. For solar system sources it should be corrected for light-time. For non-solar-system objects, the position vector defines a direction only, with arbitrary magnitude. vel_src [AU/day] Velocity vector of object with respect to solar system barycenter. vel_obs [AU/day] Velocity vector of observer with respect to solar system barycenter. d_obs_geo [AU] Distance from observer to geocenter, or <=0.0 if gravitational blueshifting due to Earth potential around observer can be ignored. d_obs_sun [AU] Distance from observer to Sun, or <=0.0 if gravitational bluehifting due to Solar potential around observer can be ignored. d_src_sun [AU] Distance from object to Sun, or <=0.0 if gravitational redshifting due to Solar potential around source can be ignored. [out] rv [km/s] The observed radial velocity measure times the speed of light, or NAN if there was an error.

Returns: 0 if successfule, or else -1 if there was an error (errno will be set to EINVAL if any of the arguments are NULL, or to some other value to indicate the type of error).

See also: rad_vel2()

References rad_vel2().

◆ rad_vel2() double rad_vel2 ( const object *restrict source, const double * pos_emit, const double * vel_src, const double * pos_det, const double * vel_obs, double d_obs_geo, double d_obs_sun, double d_src_sun )

Predicts the radial velocity of the observed object as it would be measured by spectroscopic means. This is a modified version of the original NOVAS C 3.1 rad_vel(), to account for the different directions in which light is emitted vs in which it detected, e.g. when it is gravitationally deflected.

Radial velocity is here defined as the radial velocity measure (z) times the speed of light. For major planets (and Sun and Moon), it includes gravitational corrections for light originating at the surface and observed from near Earth or else from a large distance away. For other solar system bodies, it applies to a fictitious emitter at the center of the observed object, assumed massless (no gravitational red shift). The corrections do not in general apply to reflected light. For stars, it includes all effects, such as gravitational redshift, contained in the catalog barycentric radial velocity measure, a scalar derived from spectroscopy. Nearby stars with a known kinematic velocity vector (obtained independently of spectroscopy) can be treated like solar system objects.

All the input arguments are BCRS quantities, expressed with respect to the ICRS axes. 'vel_src' and 'vel_obs' are kinematic velocities - derived from geometry or dynamics, not spectroscopy.

Any of the distances (last three input arguments) can be set to a negative value if the corresponding general relativistic gravitational potential term is not to be evaluated. These terms generally are important only at the meter/second level. If 'd_obs_geo' and 'd_obs_sun' are both zero, an average value will be used for the relativistic term for the observer, appropriate for an observer on the surface of the Earth. 'd_src_sun', if given, is used only for solar system objects.

NOTES:

This function is called by place() and novas_sky_pos() to calculate radial velocities along with the apparent position of the source.
For major planets (and Sun and Moon), the radial velocity includes gravitational redshift corrections for light originating at the surface, assuming it's observed from near Earth or else from a large distance away.

REFERENCES:

Lindegren & Dravins (2003), Astronomy & Astrophysics 401, 1185-1201.

Parameters: source Celestial object observed pos_emit [AU|*] position vector of object with respect to observer in the direction that light was emitted from the source. For solar system sources it should be corrected for light-time. For non-solar-system objects, the position vector defines a direction only, with arbitrary magnitude. vel_src [AU/day] Velocity vector of object with respect to solar system barycenter. pos_det [AU|*] apparent position vector of source, as seen by the observer. It may be the same vector as pos_emit, in which case the routine behaves like the original NOVAS_C rad_vel(). vel_obs [AU/day] Velocity vector of observer with respect to solar system barycenter. d_obs_geo [AU] Distance from observer to geocenter, or <=0.0 if gravitational blueshifting due to Earth potential around observer can be ignored. d_obs_sun [AU] Distance from observer to Sun, or <=0.0 if gravitational bluehifting due to Solar potential around observer can be ignored. d_src_sun [AU] Distance from object to Sun, or <=0.0 if gravitational redshifting due to Solar potential around source can be ignored. Additionally, a value <0 will also skip corrections for light originating at the surface of the observed major solar-system body.

Returns: [km/s] The observed radial velocity measure times the speed of light, or NAN if there was an error (errno will be set to EINVAL if any of the arguments are NULL, or to some other value to indicate the type of error).

See also: rad_vel(); place(); novas_sky_pos(); novas_v2z()

Since: 1.1

Author: Attila Kovacs

References cat_entry::dec, NOVAS_CATALOG_OBJECT, NOVAS_EARTH_RADIUS, NOVAS_EPHEM_OBJECT, NOVAS_KMS, NOVAS_ORBITAL_OBJECT, NOVAS_PLANET, NOVAS_PLANET_GRAV_Z_INIT, NOVAS_PLANETS, NOVAS_SOLAR_RADIUS, novas_vlen(), novas_z2v(), cat_entry::parallax, cat_entry::ra, and cat_entry::radialvelocity.

◆ radec2vector() int radec2vector ( double ra, double dec, double dist, double *restrict pos )

Converts equatorial spherical coordinates to a vector (equatorial rectangular coordinates).

Parameters: ra [h] Right ascension (hours). dec [deg] Declination (degrees). dist [AU] Distance (AU) [out] pos [AU] Position 3-vector, equatorial rectangular coordinates (AU).

Returns: 0 if successful, or -1 if the vector argument is NULL.

See also: vector2radec(); starvectors()

◆ radec_planet() int radec_planet ( double jd_tt, const object *restrict ss_body, const observer *restrict obs, double ut1_to_tt, enum novas_reference_system sys, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis, double *restrict rv )

Computes the place of a solar system body at the specified time for an observer in the specified coordinate system. This is the same as calling place() with the same arguments, except the different set of return values used.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Parameters: jd_tt [day] Terretrial Time (TT) based Julian date. ss_body Pointer to structure containing the body designation for the solar system body. obs Observer location. It may be NULL if not relevant. ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. sys Coordinate reference system in which to produce output values accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Topocentric apparent right ascension in hours, referred to the true equator and equinox of date, or NAN when returning with an error code. (It may be NULL if not required) [out] dec [deg] Topocentric apparent declination in degrees referred to the true equator and equinox of date, or NAN when returning with an error code. (It may be NULL if not required) [out] dis [AU] True distance from Earth to the body at 'jd_tt' in AU, or NAN when returning with an error code. (It may be NULL if not needed). [out] rv [AU/day] radial velocity relative ot observer, or NAN when returning with an error code. (It may be NULL if not required)

Returns: 0 if successful, or -1 if the object argument is NULL or if the value of 'where' in structure 'location' is invalid, or 10 + the error code from place().

See also: radec_star()

Since: 1.0

Author: Attila Kovacs

References sky_pos::dec, sky_pos::dis, NOVAS_EPHEM_OBJECT, NOVAS_ORBITAL_OBJECT, NOVAS_PLANET, place(), sky_pos::ra, sky_pos::rv, and SKY_POS_INIT.

◆ radec_star()

Computes the place of a star at date 'jd_tt', for an observer in the specified coordinate system, given the star's ICRS catalog place, proper motion, parallax, and radial velocity.

Notwithstanding the different set of return values, this is the same as calling place_star() with the same arguments.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992), Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. obs Observer location. It may be NULL if not relevant. ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. sys Coordinate reference system in which to produce output values accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Topocentric right ascension in hours, referred to true equator and equinox of date 'jd_tt' or NAN when returning with an error code. (It may be NULL if not required) [out] dec [deg] Topocentric declination in degrees, referred to true equator and equinox of date 'jd_tt' or NAN when returning with an error code. (It may be NULL if not required) [out] rv [AU/day] radial velocity relative ot observer, or NAN when returning with an error code. (It may be NULL if not required)

Returns: 0 if successful, -1 if a required pointer argument is NULL, or else 20 + the error code from place_star().

See also: radec_planet()

Since: 1.0

Author: Attila Kovacs

References sky_pos::dec, place_star(), sky_pos::ra, sky_pos::rv, and SKY_POS_INIT.

◆ redshift_vrad() double redshift_vrad ( double vrad, double z )

Applies an incremental redshift correction to a radial velocity. For example, you may use this function to correct a radial velocity calculated by rad_vel() or rad_vel2() for a Solar-system body to account for the gravitational redshift for light originating at a specific distance away from the body. For the Sun, you may want to undo the redshift correction applied for the photosphere using unredshift_vrad() first.

Parameters: vrad [km/s] Radial velocity z Redshift correction to apply

Returns: [km/s] The redshift corrected radial velocity or NAN if the redshift value is invalid (errno will be set to EINVAL).

See also: unredshift_vrad(); grav_redshift(); novas_z_add()

Since: 1.2

Author: Attila Kovacs

References novas_v2z(), and novas_z2v().

◆ refract()

Computes atmospheric optical refraction for an observed (already refracted!) zenith distance through the atmosphere. In other words this is suitable to convert refracted zenith angles to astrometric (unrefracted) zenith angles. For the reverse, see refract_astro().

The returned value is the approximate refraction for optical wavelengths. This function can be used for planning observations or telescope pointing, but should not be used for precise positioning.

NOTES:

The standard temeperature model includes a very rough estimate of the mean annual temeprature for the ovserver's latitude and elevation, rather than the 10 C everywhere assumption in NOVAS C 3.1.<.li>

REFERENCES:

Explanatory Supplement to the Astronomical Almanac, p. 144.
Bennett, G. (1982), Journal of Navigation (Royal Institute) 35, pp. 255-259.

Parameters: location Pointer to structure containing observer's location. It may also contains weather data (optional) for the observer's location. Some, but not all, refraction models will use location-based (e.g. weather) information. For models that do not need it, it may be NULL. model The built in refraction model to use. E.g. NOVAS_STANDARD_ATMOSPHERE (1), or NOVAS_WEATHER_AT_LOCATION (2)... zd_obs [deg] Observed (already refracted!) zenith distance through the atmosphere.

Returns: [deg] the calculated optical refraction or 0.0 if the location is NULL or the option is invalid or the 'zd_obs' is invalid (<90°).

See also: refract_astro(); hor_to_itrs()

References NOVAS_NO_ATMOSPHERE, NOVAS_RADIO_REFRACTION, novas_radio_refraction(), NOVAS_REFRACT_OBSERVED, NOVAS_REFRACTION_MODELS, NOVAS_WAVE_REFRACTION, novas_wave_refraction(), and NOVAS_WEATHER_AT_LOCATION.

◆ refract_astro()

Computes atmospheric optical refraction for a source at an astrometric zenith distance (e.g. calculated without accounting for an atmosphere). This is suitable for converting astrometric (unrefracted) zenith angles to observed (refracted) zenith angles. See refract() for the reverse correction.

The returned value is the approximate refraction for optical wavelengths. This function can be used for planning observations or telescope pointing, but should not be used for precise positioning.

REFERENCES:

Explanatory Supplement to the Astronomical Almanac, p. 144.
Bennett, G. (1982), Journal of Navigation (Royal Institute) 35, pp. 255-259.

Parameters: location Pointer to structure containing observer's location. It may also contains weather data (optional) for the observer's location. Some, but not all, refraction models will use location-based (e.g. weather) information. For models that do not need it, it may be NULL. model The built in refraction model to use. E.g. NOVAS_STANDARD_ATMOSPHERE (1), or NOVAS_WEATHER_AT_LOCATION (2)... zd_astro [deg] Astrometric (unrefracted) zenith distance angle of the source.

Returns: [deg] the calculated optical refraction. (to ~0.1 arcsec accuracy), or 0.0 if the location is NULL or the option is invalid.

See also: refract(); itrs_to_hor()

Since: 1.0

Author: Attila Kovacs

References novas_inv_max_iter, NOVAS_RADIO_REFRACTION, novas_radio_refraction(), NOVAS_REFRACT_ASTROMETRIC, and refract().

◆ set_cio_locator_file() int set_cio_locator_file ( const char *restrict filename )

Sets the CIO interpolaton data file to use to interpolate CIO locations vs the GCRS. You can specify either the original CIO_RA.TXT file included in the distribution (preferred since v1.1), or else a platform-specific binary data file compiled from it via the cio_file utility (the old way).

Parameters: filename Path (preferably absolute path) CIO_RA.TXT or else to the binary cio_ra.bin data.

Returns: 0 if successful, or else -1 if the specified file does not exists or we have no permission to read it.

See also: cio_location(); gcrs_to_cirs()

Since: 1.0

Author: Attila Kovacs

◆ set_nutation_lp_provider()

Set the function to use for low-precision IAU 2000 nutation calculations instead of the default nu2000k().

Parameters: func the new function to use for low-precision IAU 2000 nutation calculations

Returns: 0 if successful, or -1 if the input argument is NULL

See also: get_nutation_lp_provider(); nutation_angles()

Since: 1.0

Author: Attila Kovacs

◆ sidereal_time()

Computes the Greenwich sidereal time, either mean or apparent, at the specified Julian date. The Julian date can be broken into two parts if convenient, but for the highest precision, set 'jd_high' to be the integral part of the Julian date, and set 'jd_low' to be the fractional part.

NOTES:

Contains fix for known sidereal time units bug.

REFERENCES:

Kaplan, G. (2005), US Naval Observatory Circular 179.

Parameters: jd_ut1_high [day] High-order part of UT1 Julian date. jd_ut1_low [day] Low-order part of UT1 Julian date. (You can leave it at zero if 'jd_high' specified the date with sufficient precision) ut1_to_tt [s] TT - UT1 Time difference in seconds gst_type NOVAS_MEAN_EQUINOX (0) or NOVAS_TRUE_EQUINOX (1), depending on whether wanting mean or apparent GST, respectively. erot EROT_ERA (0) or EROT_GST (1), depending on whether to use GST relative to equinox of date (pre IAU 2006) or ERA relative to the CIO (IAU 2006 standard). accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] gst [h] Greenwich (mean or apparent) sidereal time, in hours [0:24]. (In case the returned error code is >1 the gst value will be set to NAN.)

Returns: 0 if successful, or -1 if the 'gst' argument is NULL, 1 if 'accuracy' is invalid 2 if 'method' is invalid, or else 10–30 with 10 + the error from cio_location().

See also: novas_time_gst(); era(); tod_to_itrs(); itrs_to_tod(); cel_pole(); get_ut1_to_tt()

References cio_basis(), cio_location(), e_tilt(), era(), EROT_ERA, EROT_GST, NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NOVAS_TRUE_EQUINOX, and tod_to_gcrs().

◆ spin() int spin ( double angle, const double * in, double * out )

Transforms a vector from one coordinate system to another with same origin and axes rotated about the z-axis.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: angle [deg] Angle of coordinate system rotation, positive counterclockwise when viewed from +z, in degrees. in Input position vector. [out] out Position vector expressed in new coordinate system rotated about z by 'angle'. It can be the same vector as the input.

Returns: 0 if successful, or -1 if the output vector is NULL.

References TWOPI.

◆ starvectors() int starvectors ( const cat_entry *restrict star, double *restrict pos, double *restrict motion )

Converts angular quantities for stars to vectors.

NOTES:

The velocity returned should not be used for deriving spectroscopic radial velocity. It is a measure of the perceived change of the stars position, not a true physical velocity.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: star Pointer to catalog entry structure containing ICRS catalog [out] pos [AU] Position vector, equatorial rectangular coordinates, components in AU. It may be NULL if not required. [out] motion [AU/day] Perceived motion of star, in equatorial rectangular coordinates, components in AU/Day. It must be distinct from the pos output vector, and may be NULL if not required. Note, that it is suitable only for calculating the apparent 3D location of the star at a different time, and should not be used as a measure of physical velocity, e.g. for spectroscopic radial velocity determination.

Returns: 0 if successful, or -1 if the star argument is NULL or the output vectors are the same pointer.

See also: make_cat_entry()

References NOVAS_KMS, novas_los_to_xyz(), and radec2vector().

◆ tdb2tt() int tdb2tt ( double jd_tdb, double *restrict jd_tt, double *restrict secdiff )

Computes the Terrestrial Time (TT) based Julian date corresponding to a Barycentric Dynamical Time (TDB) Julian date, and retuns th TDB-TT time difference also. It has a maximum error of 10 μs between for dates 1600 and 2200.

This function is wrapped by tt2tdb(), which is typically a lot easier to use as it returns the time difference directly, which can then be used to convert time in both directions with greater ease. For exable to convert a TT-based date to a TDB-based date:

double

TDB = TT +

tt2tdb

(TT) / 86400.0;

double tt2tdb(double jd_tt)

Definition timescale.c:178

is equivalent to:

double dt;

double TDB = TT + dt / 86400.0;

int tdb2tt(double jd_tdb, double *restrict jd_tt, double *restrict secdiff)

Definition timescale.c:133

NOTES:

This function caches the results of the last calculation in case it may be re-used at no extra computational cost for the next call.

REFERENCES:

Fairhead, L. & Bretagnon, P. (1990) Astron. & Astrophys. 229, 240.
Kaplan, G. (2005), US Naval Observatory Circular 179.

Parameters: jd_tdb [day] Barycentric Dynamic Time (TDB) based Julian date. [out] jd_tt [day] Terrestrial Time (TT) based Julian date. (It may be NULL if not required) [out] secdiff [s] Difference 'tdb_jd'-'tt_jd', in seconds. (It may be NULL if not required)

Returns: 0

See also: tt2tdb()

References NOVAS_JD_J2000.

◆ ter2cel()

Rotates a vector from the terrestrial to the celestial system. Specifically, it transforms a vector in the ITRS (rotating earth-fixed system) to the True of Date (TOD), CIRS, or GCRS (a local space-fixed system) by applying rotations for polar motion, Earth rotation (for TOD); and nutation, precession, and the dynamical-to-GCRS frame tie (for GCRS).

If 'system' is NOVAS_CIRS then method EROT_ERA must be used. Similarly, if 'system' is NOVAS_TOD then method must be EROT_ERA. Otherwise an error 3 is returned.

If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.

Deprecated:: This function can be confusing to use due to the output coordinate system being specified by a combination of two options. Use itrs_to_cirs() or itrs_to_tod() instead. You can then follow these with other conversions to GCRS (or whatever else) as appropriate.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Kaplan, G. H. (2003), 'Another Look at Non-Rotating Origins', Proceedings of IAU XXV Joint Discussion 16.

Parameters: jd_ut1_high [day] High-order part of UT1 Julian date. jd_ut1_low [day] Low-order part of UT1 Julian date. ut1_to_tt [s] TT - UT1 Time difference in seconds erot EROT_ERA (0) or EROT_GST (1), depending on whether to use GST relative to equinox of date (pre IAU 2006) or ERA relative to the CIO (IAU 2006 standard) as the Earth rotation measure. The main effect of this option is that it selects the output coordinate system as CIRS or TOD if the output coordinate class is NOVAS_DYNAMICAL_CLASS. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) coordType Output coordinate class NOVAS_REFERENCE_CLASS (0, or any value other than 1) or NOVAS_DYNAMICAL_CLASS (1). Use the former if the output coordinates are to be in the GCRS, and the latter if they are to be in CIRS or TOD (the 'erot' parameter selects which dynamical system to use for the output.) xp [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. in Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system) in the normal case where 'option' is NOVAS_GCRS (0). [out] out Position vector, equatorial rectangular coordinates in the specified output system (GCRS if 'class' is NOVAS_REFERENCE_CLASS; or else either CIRS if 'erot' is EROT_ERA, or TOD if 'erot' is EROT_GST). It may be the same vector as the input.

Returns: 0 if successful, -1 if either of the vector arguments is NULL, 1 if 'accuracy' is invalid, 2 if 'method' is invalid 10–20, or else 10 + the error from cio_location(), or 20 + error from cio_basis().

See also: itrs_to_cirs(); cirs_to_gcrs(); itrs_to_tod(); tod_to_j2000(); frame_tie(); cel2ter()

References cirs_to_gcrs(), era(), EROT_ERA, EROT_GST, NOVAS_DYNAMICAL_CLASS, NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NOVAS_TRUE_EQUINOX, sidereal_time(), spin(), tod_to_gcrs(), wobble(), WOBBLE_ITRS_TO_PEF, and WOBBLE_ITRS_TO_TIRS.

◆ terra() int terra ( const on_surface *restrict location, double lst, double *restrict pos, double *restrict vel )

Computes the position and velocity vectors of a terrestrial observer with respect to the center of the Earth.

This function ignores polar motion, unless the observer's longitude and latitude have been corrected for it, and variation in the length of day (angular velocity of earth).

The true equator and equinox of date do not form an inertial system. Therefore, with respect to an inertial system, the very small velocity component (several meters/day) due to the precession and nutation of the Earth's axis is not accounted for here.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: location Location of observer in Earth's rotating frame lst [h] Local apparent sidereal time at reference meridian in hours. [out] pos [AU] Position vector of observer with respect to center of Earth, equatorial rectangular coordinates, referred to true equator and equinox of date, components in AU. If reference meridian is Greenwich and 'lst' = 0, 'pos' is effectively referred to equator and Greenwich. (It may be NULL if no position data is required). [out] vel [AU/day] Velocity vector of observer with respect to center of Earth, equatorial rectangular coordinates, referred to true equator and equinox of date, components in AU/day. (It must be distinct from the pos output vector, and may be NULL if no velocity data is required).

Returns: 0 if successful, or -1 if location is NULL or if the pos and vel output arguments are identical pointers.

See also: make_on_surface(); geo_posvel(); sidereal_time()

References NOVAS_KM.

◆ tod_to_cirs() int tod_to_cirs ( double jd_tt, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from the True of Date (TOD) reference system to the Celestial Intermediate Reference System (CIRS) at the given epoch to the .

NOTES:

The accuracy of the output CIRS coordinates depends on how the input TOD coordinates were obtained. If TOD was calculated via the old (pre IAU 2006) method, using the Lieske et al. 1997 nutation model, then the limited accuracy of that model will affect the resulting coordinates. This is the case for the SuperNOVAS functions novas_geom_posvel() and novas_sky_pos() also, when called with NOVAS_TOD as the system, as well as all legacy NOVAS C functions that produce TOD coordinates.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in CIRS Input (x, y, z) position or velocity vector [out] out Output position or velocity 3-vector in the True of Date (TOD) frame. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL or the accuracy is invalid, or 10 + the error from cio_location(), or else 20 + the error from cio_basis().

See also: cirs_to_tod(); app_to_cirs_ra(); tod_to_gcrs(); tod_to_j2000(); tod_to_itrs()

Since: 1.1

Author: Attila Kovacs

References cio_ra(), and spin().

◆ tod_to_gcrs() int tod_to_gcrs ( double jd_tdb, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from True of Date (TOD) reference frame at the given epoch to the Geocentric Celestial Reference System(GCRS)

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date that defines the input epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in Input (x, y, z) position or velocity 3-vector in the True equinox of Date coordinate frame. [out] out Output GCRS position or velocity vector. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL.

See also: j2000_to_tod(); tod_to_cirs(); tod_to_j2000(); tod_to_itrs()

Since: 1.2

Author: Attila Kovacs

References frame_tie(), J2000_TO_ICRS, and tod_to_j2000().

◆ tod_to_itrs() int tod_to_itrs ( double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double * in, double * out )

Rotates a position vector from the dynamical True of Date (TOD) frame of date the Earth-fixed ITRS frame (pre IAU 2000 method).

If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Kaplan, G. H. (2003), 'Another Look at Non-Rotating Origins', Proceedings of IAU XXV Joint Discussion 16.

Parameters: jd_tt_high [day] High-order part of Terrestrial Time (TT) based Julian date. jd_tt_low [day] Low-order part of Terrestrial Time (TT) based Julian date. ut1_to_tt [s] TT - UT1 Time difference in seconds. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) xp [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. in Position vector, geocentric equatorial rectangular coordinates, referred to True of Date (TOD) axes (celestial system). [out] out Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system).

Returns: 0 if successful, -1 if either of the vector arguments is NULL, 1 if 'accuracy' is invalid, 2 if 'method' is invalid 10–20, 3 if the method and option are mutually incompatible, or else 10 + the error from cio_location(), or 20 + error from cio_basis().

See also: cirs_to_itrs(); itrs_to_tod(); j2000_to_tod(); tod_to_gcrs(); tod_to_j2000(); tod_to_cirs()

Since: 1.0

Author: Attila Kovacs

References cel2ter(), EROT_GST, and NOVAS_DYNAMICAL_CLASS.

◆ tod_to_j2000() int tod_to_j2000 ( double jd_tdb, enum novas_accuracy accuracy, const double * in, double * out )

Transforms a rectangular equatorial (x, y, z) vector from True of Date (TOD) reference frame at the given epoch to the J2000 coordinates.

Parameters: jd_tdb [day] Barycentric Dynamical Time (TDB) based Julian date that defines the input epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) in Input (x, y, z) position or velocity 3-vector in the True equinox of Date coordinate frame. [out] out Output position or velocity vector in rectangular equatorial coordinates at J2000. It can be the same vector as the input.

Returns: 0 if successful, or -1 if either of the vector arguments is NULL or the 'accuracy' is invalid.

See also: j2000_to_tod(); j2000_to_gcrs(); tod_to_gcrs(); tod_to_cirs(); tod_to_itrs()

Since: 1.0

Author: Attila Kovacs

References NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NUTATE_TRUE_TO_MEAN, nutation(), and precession().

◆ topo_planet() short topo_planet ( double jd_tt, const object *restrict ss_body, double ut1_to_tt, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis )

Computes the topocentric apparent place of a solar system body at the specified time. This is the same as calling place() for the body for the same observer location and NOVAS_TOD as the reference system, except the different set of return values used.

NOTES:

This call uses the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C function.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Deprecated:: Using place() with system NOVAS_CIRS is now preferred for topocentric calculations, especially when high precision is required. However, you will have to follow the IAU 2000 method consistently to produce equivalent calculations throughout.

Parameters: jd_tt [day] Terretrial Time (TT) based Julian date. ss_body Pointer to structure containing the body designation for the solar system body. ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. position Position of the observer accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Topocentric apparent right ascension in hours, referred to the true equator and equinox of date. (It may be NULL if not required) [out] dec [deg] Topocentric apparent declination in degrees referred to the true equator and equinox of date. (It may be NULL if not required) [out] dis [AU] True distance from Earth to the body at 'jd_tt' in AU (may be NULL if not needed).

Returns: 0 if successful, or -1 if the object argument is NULL, or else 1 if the value of 'where' in structure 'location' is invalid, or 10 + the error code from place().

See also: app_planet(); local_planet(); topo_planet(); virtual_planet(); astro_star(); get_ut1_to_tt()

References make_observer(), NOVAS_OBSERVER_ON_EARTH, NOVAS_TOD, and radec_planet().

◆ topo_star() short topo_star ( double jd_tt, double ut1_to_tt, const cat_entry *restrict star, const on_surface *restrict position, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec )

Computes the topocentric (True of Date; TOD) apparent place of a star at date 'jd_tt', given its ICRS catalog place, proper motion, parallax, and radial velocity.

Notwithstanding the different set of return values, this is the same as calling place_star() with the same observer location and NOVAS_TOD for an object that specifies the star.

NOTES:

This call uses the less precise old (pre IAU 2006) method is used, with the Lieske et al. 1977 nutation model, matching the behavior of the original NOVAS C function.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992), Chapter 3.

Deprecated:: Using place() with system NOVAS_CIRS is now preferred for topocentric calculations, especially when high precision is required. However, you will have to follow the IAU 2000 method consistently to produce equivalent calculations throughout.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. ut1_to_tt [s] Difference TT-UT1 at 'jd_tt', in seconds of time. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. position Position of the observer accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Topocentric right ascension in hours, referred to true equator and equinox of date 'jd_tt'. (It may be NULL if not required) [out] dec [deg] Topocentric declination in degrees, referred to true equator and equinox of date 'jd_tt'. (It may be NULL if not required)

Returns: 0 if successful, -1 if a required pointer argument is NULL, or else 20 + the error code from place_star().

See also: place_star(); app_star(); local_star(); topo_star(); virtual_star(); astro_planet(); get_ut1_to_tt()

References make_observer(), NOVAS_OBSERVER_ON_EARTH, NOVAS_TOD, and radec_star().

◆ transform_cat()

Transform a star's catalog quantities for a change the coordinate system and/or the date for which the positions are calculated. Also used to rotate catalog quantities on the dynamical equator and equinox of J2000.0 to the ICRS or vice versa.

'date_incat' and 'date_newcat' may be specified either as a Julian date (e.g., 2433282.5 or NOVAS_JD_B1950) or a fractional Julian year and fraction (e.g., 1950.0). Values less than 10000 are assumed to be years. You can also use the supplied constants NOVAS_JD_J2000 or NOVAS_JD_B1950. The date arguments are ignored for the ICRS frame conversion options.

If 'option' is PROPER_MOTION (1), input data can be in any reference system. If 'option' is PRECESSION (2) or CHANGE_EPOCH (3), input data is assume to be in the dynamical system of 'date_incat' and produces output in the dynamical system of 'date_outcat'. If 'option' is CHANGE_J2000_TO_ICRS (4), the input data should be in the J2000.0 dynamical frame. And if 'option' is CHANGE_ICRS_TO_J2000 (5), the input data must be in the ICRS, and the output will be in the J2000 dynamical frame.

This function cannot be properly used to bring data from old star catalogs into the modern system, because old catalogs were compiled using a set of constants that are incompatible with modern values. In particular, it should not be used for catalogs whose positions and proper motions were derived by assuming a precession constant significantly different from the value implicit in function precession().

Parameters: option Type of transformation jd_tt_in [day|yr] Terrestrial Time (TT) based Julian date, or year, of input catalog data. Not used if option is CHANGE_J2000_TO_ICRS (4) or CHANGE_ICRS_TO_J2000 (5). in An entry from the input catalog, with units as given in the struct definition jd_tt_out [day|yr] Terrestrial Time (TT) based Julian date, or year, of output catalog data. Not used if option is CHANGE_J2000_TO_ICRS (4) or CHANGE_ICRS_TO_J2000 (5). out_id Catalog identifier (0 terminated). It may also be NULL in which case the catalog name is inherited from the input. [out] out The transformed catalog entry, with units as given in the struct definition. It may be the same as the input.

Returns: 0 if successful, -1 if either vector argument is NULL or if the 'option' is invalid, or else 2 if 'out_id' is too long.

See also: transform_hip(); make_cat_entry(); novas_epoch(); NOVAS_JD_J2000; NOVAS_JD_B1950; NOVAS_JD_HIP

References cat_entry::catalog, CHANGE_EPOCH, CHANGE_ICRS_TO_J2000, CHANGE_J2000_TO_ICRS, cat_entry::dec, frame_tie(), ICRS_TO_J2000, J2000_TO_ICRS, NOVAS_JD_J2000, NOVAS_KMS, novas_los_to_xyz(), novas_vlen(), novas_xyz_to_los(), cat_entry::parallax, PRECESSION, precession(), cat_entry::promodec, cat_entry::promora, PROPER_MOTION, cat_entry::ra, radec2vector(), cat_entry::radialvelocity, SIZE_OF_CAT_NAME, SIZE_OF_OBJ_NAME, cat_entry::starname, and cat_entry::starnumber.

◆ transform_hip()

Convert Hipparcos catalog data at epoch J1991.25 to epoch J2000.0, for use within NOVAS. To be used only for Hipparcos or Tycho stars with linear space motion. Both input and output data is in the ICRS.

Parameters: hipparcos An entry from the Hipparcos catalog, at epoch J1991.25, with 'ra' in degrees(!) as per Hipparcos catalog units. [out] hip_2000 The transformed input entry, at epoch J2000.0, with 'ra' in hours(!) as per the NOVAS convention. It may be the same as the input.

Returns: 0 if successful, or -1 if either of the input pointer arguments is NULL.

See also: make_cat_entry(); NOVAS_JD_HIP

References cat_entry::catalog, NOVAS_JD_HIP, cat_entry::ra, and transform_cat().

◆ tt2tdb() double tt2tdb ( double jd_tt )

Returns the TDB - TT time difference in seconds for a given TT or TDB date, with a maximum error of 10 μs for dates between 1600 and 2200.

REFERENCES

Fairhead, L. & Bretagnon, P. (1990) Astron. & Astrophys. 229, 240.
Kaplan, G. (2005), US Naval Observatory Circular 179.
Moyer, T.D. (1981), Celestial mechanics, Volume 23, Issue 1, pp. 57-68<.li>

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date, but Barycentri Dynamical Time (TDB) can also be used here without any loss of precision on the result.

Returns: [s] TDB - TT time difference.

See also: tt2tdb_hp(); tt2tdb_fp(); tdb2tt()

Since: 1.0

Author: Attila Kovacs

References tdb2tt().

◆ tt2tdb_fp() double tt2tdb_fp ( double jd_tt, double limit )

Returns the TDB-TT time difference with flexible precision. This implementation uses the series expansion by Fairhead & Bretagnon 1990, terminating theterm at or below the specified limiting amplitude.

REFERENCES:

Fairhead, L., & Bretagnon, P. (1990) A&A, 229, 240

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date, but Barycentric Dynamical Time (TDB) limit [us] Amplitude of limiting term to include in series. 0 or negative values will include all terms, producing the same result as tt2tdb_hp().

Returns: [s] TDB - TT time difference.

Since: 1.4

Author: Attila Kovacs

See also: tt2tdb_hp(); tt2tdb()

References NOVAS_JD_J2000.

◆ tt2tdb_hp() double tt2tdb_hp ( double jd_tt )

Returns the TDB-TT time difference with flexible precision. This implementation uses the full series expansion by Fairhead & Bretagnon 1990, resulting in an accuracy below 100 ns.

REFERENCES:

Fairhead, L., & Bretagnon, P. (1990) A&A, 229, 240

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date, but Barycentric Dynamical Time (TDB)

Returns: [s] TDB - TT time difference.

Since: 1.4

Author: Attila Kovacs

See also: tt2tdb_fp(); tt2tdb()

References tt2tdb_fp().

◆ unredshift_vrad() double unredshift_vrad ( double vrad, double z )

Undoes an incremental redshift correction that was applied to radial velocity.

Parameters: vrad [km/s] Radial velocity z Redshift correction to apply

Returns: [km/s] The radial velocity without the redshift correction or NAN if the redshift value is invalid. (errno will be set to EINVAL)

See also: redshift_vrad(); grav_redshift()

Since: 1.2

Author: Attila Kovacs

References novas_v2z(), and novas_z2v().

◆ vector2radec() short vector2radec ( const double *restrict pos, double *restrict ra, double *restrict dec )

Converts an vector in equatorial rectangular coordinates to equatorial spherical coordinates.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.

Parameters: pos Position 3-vector, equatorial rectangular coordinates. [out] ra [h] Right ascension in hours [0:24] or NAN if the position vector is NULL or a null-vector. It may be NULL if notrequired. [out] dec [deg] Declination in degrees [-90:90] or NAN if the position vector is NULL or a null-vector. It may be NULL if not required.

Returns: 0 if successful, -1 of any of the arguments are NULL, or 1 if all input components are 0 so 'ra' and 'dec' are indeterminate, or else 2 if both x and y are zero, but z is nonzero, and so 'ra' is indeterminate.

See also: radec2vector()

◆ virtual_planet() short virtual_planet ( double jd_tt, const object *restrict ss_body, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec, double *restrict dis )

Computes the virtual place of a solar system body, referenced to the GCRS. This is the same as calling place_gcrs() for the body, except the different set of return values used.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992),Chapter 3.

Parameters: jd_tt [day] Terretrial Time (TT) based Julian date. ss_body Pointer to structure containing the body designation for the solar system body. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Virtual right ascension in hours, referred to the GCRS (it may be NULL if not required). [out] dec [deg] Virtual declination in degrees, referred to the GCRS (it may be NULL if not required). [out] dis [AU] True distance from Earth to the body at 'jd_tt' in AU (can be NULL if not needed).

Returns: 0 if successful, or -1 if the object argument is NULL, or else 1 if the value of 'type' in structure 'ss_body' is invalid, or 10 + the error code from place().

See also: place_gcrs(); app_planet(); astro_planet(); local_planet(); topo_planet(); app_star()

References NOVAS_GCRS, and radec_planet().

◆ virtual_star() short virtual_star ( double jd_tt, const cat_entry *restrict star, enum novas_accuracy accuracy, double *restrict ra, double *restrict dec )

Computes the virtual place of a star, referenced to GCRS, at date 'jd_tt', given its catalog mean place, proper motion, parallax, and radial velocity.

Notwithstanding the different set of return values, this is the same as calling place_star() with a NULL observer location and NOVAS_GCRS as the system, or place_gcrs() for an object that specifies the star.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Explanatory Supplement to the Astronomical Almanac (1992), Chapter 3.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. star Pointer to catalog entry structure containing catalog data for the object in the ICRS. accuracy NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) [out] ra [h] Virtual right ascension in hours, referred to the GCRS (it may be NULL if not required). [out] dec [deg] Virtual declination in degrees, referred to the GCRS (it may be NULL if not required).

Returns: 0 if successful, or -1 if a required pointer argument is NULL, or 20 + the error from place().

See also: place_star(); place_gcrs(); app_star(); astro_star(); local_star(); topo_star(); virtual_planet()

References NOVAS_GCRS, and radec_star().

◆ wobble() int wobble ( double jd_tt, enum novas_wobble_direction direction, double xp, double yp, const double * in, double * out )

Corrects a vector in the ITRS (rotating Earth-fixed system) for polar motion, and also corrects the longitude origin (by a tiny amount) to the Terrestrial Intermediate Origin (TIO). The ITRS vector is thereby transformed to the Terrestrial Intermediate Reference System (TIRS) or Pseudo Earth Fixed (PEF), based on the true (rotational) equator and TIO; or vice versa. Because the true equator is the plane orthogonal to the direction of the Celestial Intermediate Pole (CIP), the components of the output vector are referred to z and x axes toward the CIP and TIO, respectively.

NOTES:

Generally, this function should not be called if global pole offsets were set via cel_pole() and then used via place() or one of its variants to calculate Earth orientation corrected (TOD or CIRS) apparent coordinates. In such cases, calling wobble() would apply duplicate corrections. It is generally best to forgo using cel_pole() going forward, and instead apply Earth orinetation corrections with wobble() only when converting vectors to the Earth-fixed ITRS frame.

REFERENCES:

Kaplan, G. H. et. al. (1989). Astron. Journ. 97, 1197-1210.
Lambert & Bizouard (2002), Astronomy and Astrophysics 394, 317-321.

Parameters: jd_tt [day] Terrestrial Time (TT) based Julian date. direction WOBBLE_ITRS_TO_TIRS (0) or WOBBLE_TIRS_TO_ITRS (1) to include corrections for the TIO's longitude (IAU 2006 method); or else WOBBLE_ITRS_TO_PEF (2) or WOBBLE_PEF_TO_ITRS (3) to correct for dx, dy but not for the TIO's longitude (old, pre IAU 2006 method). Negative values default to WOBBLE_TIRS_TO_ITRS. xp [arcsec] Conventionally-defined X coordinate of Celestial Intermediate Pole with respect to ITRS pole, in arcseconds. yp [arcsec] Conventionally-defined Y coordinate of Celestial Intermediate Pole with respect to ITRS pole, in arcseconds. in Input position vector, geocentric equatorial rectangular coordinates, in the original system defined by 'direction' [out] out Output Position vector, geocentric equatorial rectangular coordinates, in the final system defined by 'direction'. It can be the same vector as the input.

Returns: 0 if successful, or -1 if the direction is invalid output vector argument is NULL.

See also: cel_pole(); cirs_to_itrs(); tod_to_itrs(); place(); sidereal_time(); e_tilt(); NOVAS_FULL_ACCURACY

References NOVAS_WOBBLE_DIRECTIONS, WOBBLE_ITRS_TO_PEF, WOBBLE_ITRS_TO_TIRS, and WOBBLE_TIRS_TO_ITRS.

◆ grav_bodies_full_accuracy int grav_bodies_full_accuracy extern

Current set of gravitating bodies to use for deflection calculations in full accuracy mode. Each bit signifies whether a given body is to be accounted for as a gravitating body that bends light, such as the bit (1 << NOVAS_JUPITER) indicates whether or not Jupiter is considered as a deflecting body. You should also be sure that you provide ephemeris data for bodies that are designated for the deflection calculation.

See also: grav_def(); grav_planets(); DEFAULT_GRAV_BODIES_FULL_ACCURACY; set_ephem_provider_hp()

Since: 1.1

◆ grav_bodies_reduced_accuracy int grav_bodies_reduced_accuracy extern

Current set of gravitating bodies to use for deflection calculations in reduced accuracy mode. Each bit signifies whether a given body is to be accounted for as a gravitating body that bends light, such as the bit (1 << NOVAS_JUPITER) indicates whether or not Jupiter is considered as a deflecting body. You should also be sure that you provide ephemeris data for bodies that are designated for the deflection calculation.

See also: grav_def(); grav_planets(); DEFAULT_GRAV_BODIES_REDUCED_ACCURACY; set_ephem_provider()

Since: 1.1

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4