pub fn atcc13(
rc: f64,
dc: f64,
pr: f64,
pd: f64,
px: f64,
rv: f64,
date1: f64,
date2: f64,
) -> (f64, f64)Expand description
Catalog -> astrometric.
Transform a star’s ICRS catalog entry (epoch J2000.0) into ICRS astrometric place.
This function is part of the International Astronomical Union’s SOFA (Standards of Fundamental Astronomy) software collection.
Status: support function.
Given:
rc double ICRS right ascension at J2000.0 (radians, Note 1)
dc double ICRS declination at J2000.0 (radians, Note 1)
pr double RA proper motion (radians/year, Note 2)
pd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, +ve if receding)
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 3)Returned: ra,da double* ICRS astrometric RA,Dec (radians)
Notes:
-
Star data for an epoch other than J2000.0 (for example from the Hipparcos catalog, which has an epoch of J1991.25) will require a preliminary call to iauPmsafe before use.
-
The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
-
The TDB date date1+date2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TDB)=2450123.7 could be expressed in any of these ways, among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience. For most applications of this function the choice will not be at all critical.
TT can be used instead of TDB without any significant impact on accuracy.
Called:
iauApci13 astrometry parameters, ICRS-CIRS, 2013
iauAtccq quick catalog ICRS to astrometric