atcc13¶

erfa.atcc13(rc, dc, pr, pd, px, rv, date1, date2)[source]¶

Transform a star’s ICRS catalog entry (epoch J2000.0) into ICRS astrometric place.

Parameters:

rcdouble array
dcdouble array
prdouble array
pddouble array
pxdouble array
rvdouble array
date1double array
date2double array

Returns:

radouble array
dadouble array

Notes

Wraps ERFA function eraAtcc13. The ERFA documentation is:

- - - - - - - - - -
 e r a A t c c 1 3
- - - - - - - - - -

Transform a star's ICRS catalog entry (epoch J2000.0) into ICRS
astrometric place.

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:

1) 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 eraPmsafe before use.

2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.

3) 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:
   eraApci13    astrometry parameters, ICRS-CIRS, 2013
   eraAtccq     quick catalog ICRS to astrometric

This revision:   2021 April 18

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

Navigation

atcc13¶