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/*
*+
* Name:
* palEqecl
* Purpose:
* Transform from J2000.0 equatorial coordinates to ecliptic coordinates
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* void palEqecl( double dr, double dd, double date,
* double *dl, double *db);
* Arguments:
* dr = double (Given)
* J2000.0 mean RA (radians)
* dd = double (Given)
* J2000.0 mean Dec (Radians)
* date = double (Given)
* TT as Modified Julian Date (JD-2400000.5). The difference
* between TT and TDB is of the order of a millisecond or two
* (i.e. about 0.02 arc-seconds).
* dl = double * (Returned)
* Ecliptic longitude (mean of date, IAU 1980 theory, radians)
* db = double * (Returned)
* Ecliptic latitude (mean of date, IAU 1980 theory, radians)
* Description:
* Transform from J2000.0 equatorial coordinates to ecliptic coordinates.
* Authors:
* PTW: Patrick T. Wallace
* TIMJ: Tim Jenness (JAC, Hawaii)
* {enter_new_authors_here}
* History:
* 2012-03-02 (TIMJ):
* Initial version
* Adapted with permission from the Fortran SLALIB library.
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 1995 Rutherford Appleton Laboratory
* Copyright (C) 2012 Science and Technology Facilities Council.
* All Rights Reserved.
* Licence:
* 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 3 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; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
#include "pal1sofa.h"
void palEqecl ( double dr, double dd, double date, double *dl, double *db ) {
double v1[3], v2[3];
double rmat[3][3];
/* Spherical to Cartesian */
eraS2c( dr, dd, v1 );
/* Mean J2000 to mean of date */
palPrec( 2000.0, palEpj(date), rmat );
eraRxp( rmat, v1, v2 );
/* Equatorial to ecliptic */
palEcmat( date, rmat );
eraRxp( rmat, v2, v1 );
/* Cartesian to spherical */
eraC2s( v1, dl, db );
/* Express in conventional range */
*dl = eraAnp( *dl );
*db = palDrange( *db );
}
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