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eqecl.f
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eqecl.f
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SUBROUTINE slEQEC (DR, DD, DATE, DL, DB)
*+
* - - - - - -
* E Q E C
* - - - - - -
*
* Transformation from J2000.0 equatorial coordinates to
* ecliptic coordinates (double precision)
*
* Given:
* DR,DD dp J2000.0 mean RA,Dec (radians)
* DATE dp TDB (loosely ET) as Modified Julian Date
* (JD-2400000.5)
* Returned:
* DL,DB dp ecliptic longitude and latitude
* (mean of date, IAU 1980 theory, radians)
*
* Called:
* slDS2C, slPREC, slEPJ, slDMXV, slECMA, slDC2S,
* slDA2P, slDA1P
*
* P.T.Wallace Starlink March 1986
*
* 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., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301 USA
*
* Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
*-
IMPLICIT NONE
DOUBLE PRECISION DR,DD,DATE,DL,DB
DOUBLE PRECISION slEPJ,slDA2P,slDA1P
DOUBLE PRECISION RMAT(3,3),V1(3),V2(3)
* Spherical to Cartesian
CALL slDS2C(DR,DD,V1)
* Mean J2000 to mean of date
CALL slPREC(2000D0,slEPJ(DATE),RMAT)
CALL slDMXV(RMAT,V1,V2)
* Equatorial to ecliptic
CALL slECMA(DATE,RMAT)
CALL slDMXV(RMAT,V2,V1)
* Cartesian to spherical
CALL slDC2S(V1,DL,DB)
* Express in conventional ranges
DL=slDA2P(DL)
DB=slDA1P(DB)
END