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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