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slalib/fk54z.f

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+      SUBROUTINE sla_FK54Z (R2000,D2000,BEPOCH,
+     :                      R1950,D1950,DR1950,DD1950)
+*+
+*     - - - - - -
+*      F K 5 4 Z
+*     - - - - - -
+*
+*  Convert a J2000.0 FK5 star position to B1950.0 FK4 assuming
+*  zero proper motion and parallax (double precision)
+*
+*  This routine converts star positions from the new, IAU 1976,
+*  FK5, Fricke system to the old, Bessel-Newcomb, FK4 system.
+*
+*  Given:
+*     R2000,D2000     dp    J2000.0 FK5 RA,Dec (rad)
+*     BEPOCH          dp    Besselian epoch (e.g. 1950D0)
+*
+*  Returned:
+*     R1950,D1950     dp    B1950.0 FK4 RA,Dec (rad) at epoch BEPOCH
+*     DR1950,DD1950   dp    B1950.0 FK4 proper motions (rad/trop.yr)
+*
+*  Notes:
+*
+*  1)  The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
+*
+*  2)  Conversion from Julian epoch 2000.0 to Besselian epoch 1950.0
+*      only is provided for.  Conversions involving other epochs will
+*      require use of the appropriate precession routines before and
+*      after this routine is called.
+*
+*  3)  Unlike in the sla_FK524 routine, the FK5 proper motions, the
+*      parallax and the radial velocity are presumed zero.
+*
+*  4)  It is the intention that FK5 should be a close approximation
+*      to an inertial frame, so that distant objects have zero proper
+*      motion;  such objects have (in general) non-zero proper motion
+*      in FK4, and this routine returns those fictitious proper
+*      motions.
+*
+*  5)  The position returned by this routine is in the B1950
+*      reference frame but at Besselian epoch BEPOCH.  For
+*      comparison with catalogues the BEPOCH argument will
+*      frequently be 1950D0.
+*
+*  Called:  sla_FK524, sla_PM
+*
+*  P.T.Wallace   Starlink   10 April 1990
+*
+*  Copyright (C) 1995 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 R2000,D2000,BEPOCH,
+     :                 R1950,D1950,DR1950,DD1950
+
+      DOUBLE PRECISION R,D,PX,RV
+
+
+
+*  FK5 equinox J2000 (any epoch) to FK4 equinox B1950 epoch B1950
+      CALL sla_FK524(R2000,D2000,0D0,0D0,0D0,0D0,
+     :               R,D,DR1950,DD1950,PX,RV)
+
+*  Fictitious proper motion to epoch BEPOCH
+      CALL sla_PM(R,D,DR1950,DD1950,0D0,0D0,1950D0,BEPOCH,
+     :            R1950,D1950)
+
+      END