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SuperNOVAS: src/util.c File Reference

Date

Created on Mar 6, 2025

Various commonly used routines used throughout the SuperNOVAS library.

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:

1. 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().

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

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.

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().

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()

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.

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()

(for internal use only) Calculates the length of a 3-vector

Parameters

v Pointer to a 3-component (x, y, z) vector. The argument cannot be NULL

Returns

the length of the vector

See also

vdot()

vdist()

Since

1.0

Author

Attila Kovacs

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()

Transforms a vector from one coordinate system to another with same origin and axes rotated about the z-axis.

REFERENCES:

1. 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.

Converts an vector in equatorial rectangular coordinates to equatorial spherical coordinates.

REFERENCES:

1. 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()

Maximum number of iterations for convergent inverse calculations. Most iterative inverse functions should normally converge in a handful of iterations. In some pathological cases more iterations may be required. This variable sets an absolute maximum for the number of iterations in order to avoid runaway (zombie) behaviour. If inverse functions faile to converge, they will return a value indicating an error, and errno should be set to ECANCELED.

Since

1.1

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