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87 lines
2.9 KiB
Fortran
87 lines
2.9 KiB
Fortran
SUBROUTINE sla_FK54Z (R2000,D2000,BEPOCH,
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: R1950,D1950,DR1950,DD1950)
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*+
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* - - - - - -
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* F K 5 4 Z
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* - - - - - -
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*
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* Convert a J2000.0 FK5 star position to B1950.0 FK4 assuming
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* zero proper motion and parallax (double precision)
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*
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* This routine converts star positions from the new, IAU 1976,
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* FK5, Fricke system to the old, Bessel-Newcomb, FK4 system.
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*
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* Given:
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* R2000,D2000 dp J2000.0 FK5 RA,Dec (rad)
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* BEPOCH dp Besselian epoch (e.g. 1950D0)
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*
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* Returned:
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* R1950,D1950 dp B1950.0 FK4 RA,Dec (rad) at epoch BEPOCH
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* DR1950,DD1950 dp B1950.0 FK4 proper motions (rad/trop.yr)
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*
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* Notes:
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*
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* 1) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
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*
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* 2) Conversion from Julian epoch 2000.0 to Besselian epoch 1950.0
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* only is provided for. Conversions involving other epochs will
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* require use of the appropriate precession routines before and
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* after this routine is called.
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*
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* 3) Unlike in the sla_FK524 routine, the FK5 proper motions, the
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* parallax and the radial velocity are presumed zero.
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*
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* 4) It is the intention that FK5 should be a close approximation
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* to an inertial frame, so that distant objects have zero proper
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* motion; such objects have (in general) non-zero proper motion
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* in FK4, and this routine returns those fictitious proper
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* motions.
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*
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* 5) The position returned by this routine is in the B1950
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* reference frame but at Besselian epoch BEPOCH. For
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* comparison with catalogues the BEPOCH argument will
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* frequently be 1950D0.
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*
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* Called: sla_FK524, sla_PM
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*
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* P.T.Wallace Starlink 10 April 1990
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*
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* Copyright (C) 1995 Rutherford Appleton Laboratory
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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DOUBLE PRECISION R2000,D2000,BEPOCH,
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: R1950,D1950,DR1950,DD1950
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DOUBLE PRECISION R,D,PX,RV
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* FK5 equinox J2000 (any epoch) to FK4 equinox B1950 epoch B1950
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CALL sla_FK524(R2000,D2000,0D0,0D0,0D0,0D0,
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: R,D,DR1950,DD1950,PX,RV)
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* Fictitious proper motion to epoch BEPOCH
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CALL sla_PM(R,D,DR1950,DD1950,0D0,0D0,1950D0,BEPOCH,
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: R1950,D1950)
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END
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