1 /*
2 *+
3 * Name:
4 * palEqecl
5
6 * Purpose:
7 * Transform from J2000.0 equatorial coordinates to ecliptic coordinates
8
9 * Language:
10 * Starlink ANSI C
11
12 * Type of Module:
13 * Library routine
14
15 * Invocation:
16 * void palEqecl( double dr, double dd, double date,
17 * double *dl, double *db);
18
19 * Arguments:
20 * dr = double (Given)
21 * J2000.0 mean RA (radians)
22 * dd = double (Given)
23 * J2000.0 mean Dec (Radians)
24 * date = double (Given)
25 * TT as Modified Julian Date (JD-2400000.5). The difference
26 * between TT and TDB is of the order of a millisecond or two
27 * (i.e. about 0.02 arc-seconds).
28 * dl = double * (Returned)
29 * Ecliptic longitude (mean of date, IAU 1980 theory, radians)
30 * db = double * (Returned)
31 * Ecliptic latitude (mean of date, IAU 1980 theory, radians)
32
33 * Description:
34 * Transform from J2000.0 equatorial coordinates to ecliptic coordinates.
35
36 * Authors:
37 * PTW: Patrick T. Wallace
38 * TIMJ: Tim Jenness (JAC, Hawaii)
39 * {enter_new_authors_here}
40
41 * History:
42 * 2012-03-02 (TIMJ):
43 * Initial version
44 * Adapted with permission from the Fortran SLALIB library.
45 * {enter_further_changes_here}
46
47 * Copyright:
48 * Copyright (C) 1995 Rutherford Appleton Laboratory
49 * Copyright (C) 2012 Science and Technology Facilities Council.
50 * All Rights Reserved.
51
52 * Licence:
53 * This program is free software; you can redistribute it and/or
54 * modify it under the terms of the GNU General Public License as
55 * published by the Free Software Foundation; either version 3 of
56 * the License, or (at your option) any later version.
57 *
58 * This program is distributed in the hope that it will be
59 * useful, but WITHOUT ANY WARRANTY; without even the implied
60 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
61 * PURPOSE. See the GNU General Public License for more details.
62 *
63 * You should have received a copy of the GNU General Public License
64 * along with this program; if not, write to the Free Software
65 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
66 * MA 02110-1301, USA.
67
68 * Bugs:
69 * {note_any_bugs_here}
70 *-
71 */
72
73 #include "pal.h"
74 #include "pal1sofa.h"
75
palEqecl(double dr,double dd,double date,double * dl,double * db)76 void palEqecl ( double dr, double dd, double date, double *dl, double *db ) {
77 double v1[3], v2[3];
78 double rmat[3][3];
79
80 /* Spherical to Cartesian */
81 eraS2c( dr, dd, v1 );
82
83 /* Mean J2000 to mean of date */
84 palPrec( 2000.0, palEpj(date), rmat );
85 eraRxp( rmat, v1, v2 );
86
87 /* Equatorial to ecliptic */
88 palEcmat( date, rmat );
89 eraRxp( rmat, v2, v1 );
90
91 /* Cartesian to spherical */
92 eraC2s( v1, dl, db );
93
94 /* Express in conventional range */
95 *dl = eraAnp( *dl );
96 *db = palDrange( *db );
97 }
98