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slalib/amp.f

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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