amp.f

      SUBROUTINE sla_AMP (RA, DA, DATE, EQ, RM, DM)
*+
*     - - - -
*      A M P
*     - - - -
*
*  Convert star RA,Dec from geocentric apparent to mean place
*
*  The mean coordinate system is the post IAU 1976 system,
*  loosely called FK5.
*
*  Given:
*     RA       d      apparent RA (radians)
*     DA       d      apparent Dec (radians)
*     DATE     d      TDB for apparent place (JD-2400000.5)
*     EQ       d      equinox:  Julian epoch of mean place
*
*  Returned:
*     RM       d      mean RA (radians)
*     DM       d      mean Dec (radians)
*
*  References:
*     1984 Astronomical Almanac, pp B39-B41.
*     (also Lederle & Schwan, Astron. Astrophys. 134,
*      1-6, 1984)
*
*  Notes:
*
*  1)  The distinction between the required TDB and TT is always
*      negligible.  Moreover, for all but the most critical
*      applications UTC is adequate.
*
*  2)  Iterative techniques are used for the aberration and light
*      deflection corrections so that the routines sla_AMP (or
*      sla_AMPQK) and sla_MAP (or sla_MAPQK) are accurate inverses;
*      even at the edge of the Sun's disc the discrepancy is only
*      about 1 nanoarcsecond.
*
*  3)  Where multiple apparent places are to be converted to mean
*      places, for a fixed date and equinox, it is more efficient to
*      use the sla_MAPPA routine to compute the required parameters
*      once, followed by one call to sla_AMPQK per star.
*
*  4)  The accuracy is sub-milliarcsecond, limited by the
*      precession-nutation model (IAU 1976 precession, Shirai &
*      Fukushima 2001 forced nutation and precession corrections).
*
*  5)  The accuracy is further limited by the routine sla_EVP, called
*      by sla_MAPPA, which computes the Earth position and velocity
*      using the methods of Stumpff.  The maximum error is about
*      0.3 mas.
*
*  Called:  sla_MAPPA, sla_AMPQK
*
*  P.T.Wallace   Starlink   17 September 2001
*
*  Copyright (C) 2001 Rutherford Appleton Laboratory
*
*  License:
*    This program is free software; you can redistribute it and/or modify
*    it under the terms of the GNU General Public License as published by
*    the Free Software Foundation; either version 2 of the License, or
*    (at your option) any later version.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU General Public License for more details.
*
*    You should have received a copy of the GNU General Public License
*    along with this program (see SLA_CONDITIONS); if not, write to the 
*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
*    Boston, MA  02111-1307  USA
*
*-

      IMPLICIT NONE

      DOUBLE PRECISION RA,DA,DATE,EQ,RM,DM

      DOUBLE PRECISION AMPRMS(21)



      CALL sla_MAPPA(EQ,DATE,AMPRMS)
      CALL sla_AMPQK(RA,DA,AMPRMS,RM,DM)

      END