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