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# atcc13

erfa.atcc13(rc, dc, pr, pd, px, rv, date1, date2)

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

  Parameters:
    rc double array
    dc double array
    pr double array
    pd double array
    px double array
    rv double array
    date1 double array
    date2 double array
  Returns:
    ra double array
    da double 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.