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SuperNOVAS v1.3
The NOVAS C library, made better
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Functions | |
double | accum_prec (double t) |
short | cel_pole (double jd_tt, enum novas_pole_offset_type type, double dpole1, double dpole2) |
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) |
double | ee_ct (double jd_tt_high, double jd_tt_low, enum novas_accuracy accuracy) |
int | fund_args (double t, novas_delaunay_args *restrict a) |
double | ira_equinox (double jd_tdb, enum novas_equinox_type equinox, enum novas_accuracy accuracy) |
double | mean_obliq (double jd_tdb) |
int | nutation (double jd_tdb, enum novas_nutation_direction direction, enum novas_accuracy accuracy, const double *in, double *out) |
double | planet_lon (double t, enum novas_planet planet) |
short | precession (double jd_tdb_in, const double *in, double jd_tdb_out, double *out) |
Various function for calculating the equator and equinox of date, and related quatities.
double accum_prec | ( | double | t | ) |
Returns the general precession in longitude (Simon et al. 1994), equivalent to 5028.8200 arcsec/cy at J2000.
t | [cy] Julian centuries since J2000 |
References TWOPI.
short cel_pole | ( | double | jd_tt, |
enum novas_pole_offset_type | type, | ||
double | dpole1, | ||
double | dpole2 | ||
) |
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:
wobble()
). REFERENCES:
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. |
References POLE_OFFSETS_DPSI_DEPS, and POLE_OFFSETS_X_Y.
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:
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. |
References ee_ct(), mean_obliq(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and nutation_angles().
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:
REFERENCES:
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) |
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().
int fund_args | ( | double | t, |
novas_delaunay_args *restrict | a | ||
) |
Compute the fundamental arguments (mean elements) of the Sun and Moon.
REFERENCES:
t | [cy] TDB time in Julian centuries since J2000.0 | |
[out] | a | [rad] Fundamental arguments data to populate (5 doubles) [0:2π] |
References novas_norm_ang().
double ira_equinox | ( | double | jd_tdb, |
enum novas_equinox_type | equinox, | ||
enum novas_accuracy | accuracy | ||
) |
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:
REFERENCES:
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) |
cio_location()
internally. References e_tilt(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUINOX.
double mean_obliq | ( | double | jd_tdb | ) |
Computes the mean obliquity of the ecliptic.
REFERENCES:
jd_tdb | [day] Barycentric Dynamic Time (TDB) based Julian date |
int nutation | ( | double | jd_tdb, |
enum novas_nutation_direction | direction, | ||
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out | ||
) |
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:
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. |
References e_tilt(), and NUTATE_MEAN_TO_TRUE.
double planet_lon | ( | double | t, |
enum novas_planet | planet | ||
) |
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).
t | [cy] Julian centuries since J2000 |
planet | Novas planet id, e.g. NOVAS_MARS. |
planet
id is out of range.References NOVAS_NEPTUNE, and TWOPI.
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.
REFERENCES:
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. |
References precession().