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73 lines
2.1 KiB
Fortran
73 lines
2.1 KiB
Fortran
SUBROUTINE sla_EQECL (DR, DD, DATE, DL, DB)
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*+
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* - - - - - -
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* E Q E C L
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* - - - - - -
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*
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* Transformation from J2000.0 equatorial coordinates to
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* ecliptic coordinates (double precision)
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*
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* Given:
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* DR,DD dp J2000.0 mean RA,Dec (radians)
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* DATE dp TDB (loosely ET) as Modified Julian Date
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* (JD-2400000.5)
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* Returned:
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* DL,DB dp ecliptic longitude and latitude
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* (mean of date, IAU 1980 theory, radians)
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*
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* Called:
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* sla_DCS2C, sla_PREC, sla_EPJ, sla_DMXV, sla_ECMAT, sla_DCC2S,
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* sla_DRANRM, sla_DRANGE
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*
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* P.T.Wallace Starlink March 1986
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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 DR,DD,DATE,DL,DB
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DOUBLE PRECISION sla_EPJ,sla_DRANRM,sla_DRANGE
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DOUBLE PRECISION RMAT(3,3),V1(3),V2(3)
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* Spherical to Cartesian
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CALL sla_DCS2C(DR,DD,V1)
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* Mean J2000 to mean of date
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CALL sla_PREC(2000D0,sla_EPJ(DATE),RMAT)
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CALL sla_DMXV(RMAT,V1,V2)
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* Equatorial to ecliptic
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CALL sla_ECMAT(DATE,RMAT)
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CALL sla_DMXV(RMAT,V2,V1)
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* Cartesian to spherical
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CALL sla_DCC2S(V1,DL,DB)
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* Express in conventional ranges
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DL=sla_DRANRM(DL)
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DB=sla_DRANGE(DB)
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END
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