| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * palEqgal
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| 5 |
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| 6 | * Purpose:
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| 7 | * Convert from J2000.0 equatorial coordinates to Galactic
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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 palEqgal ( double dr, double dd, double *dl, double *db );
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| 17 |
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| 18 | * Arguments:
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| 19 | * dr = double (Given)
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| 20 | * J2000.0 RA (radians)
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| 21 | * dd = double (Given)
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| 22 | * J2000.0 Dec (radians
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| 23 | * dl = double * (Returned)
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| 24 | * Galactic longitude (radians).
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| 25 | * db = double * (Returned)
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| 26 | * Galactic latitude (radians).
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| 27 |
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| 28 | * Description:
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| 29 | * Transformation from J2000.0 equatorial coordinates
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| 30 | * to IAU 1958 galactic coordinates.
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| 31 |
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| 32 | * Authors:
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| 33 | * PTW: Pat Wallace (STFC)
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| 34 | * TIMJ: Tim Jenness (JAC, Hawaii)
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| 35 | * {enter_new_authors_here}
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| 36 |
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| 37 | * Notes:
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| 38 | * The equatorial coordinates are J2000.0. Use the routine
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| 39 | * palGe50 if conversion to B1950.0 'FK4' coordinates is
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| 40 | * required.
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| 41 |
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| 42 | * See Also:
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| 43 | * Blaauw et al, Mon.Not.R.Astron.Soc.,121,123 (1960)
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| 44 |
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| 45 | * History:
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| 46 | * 2012-02-12(TIMJ):
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| 47 | * Initial version with documentation taken from Fortran SLA
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| 48 | * Adapted with permission from the Fortran SLALIB library.
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| 49 | * {enter_further_changes_here}
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| 50 |
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| 51 | * Copyright:
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| 52 | * Copyright (C) 1998 Rutherford Appleton Laboratory
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| 53 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 54 | * All Rights Reserved.
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| 55 |
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| 56 | * Licence:
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| 57 | * This program is free software: you can redistribute it and/or
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| 58 | * modify it under the terms of the GNU Lesser General Public
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| 59 | * License as published by the Free Software Foundation, either
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| 60 | * version 3 of the License, or (at your option) any later
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| 61 | * version.
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| 62 | *
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| 63 | * This program is distributed in the hope that it will be useful,
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| 64 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 65 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 66 | * GNU Lesser General Public License for more details.
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| 67 | *
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| 68 | * You should have received a copy of the GNU Lesser General
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| 69 | * License along with this program. If not, see
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| 70 | * <http://www.gnu.org/licenses/>.
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| 71 |
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| 72 | * Bugs:
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| 73 | * {note_any_bugs_here}
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| 74 | *-
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| 75 | */
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| 76 |
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| 77 | #include "pal.h"
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| 78 | #include "pal1sofa.h"
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| 79 |
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| 80 | void palEqgal ( double dr, double dd, double *dl, double *db ) {
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| 81 |
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| 82 | double v1[3];
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| 83 | double v2[3];
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| 84 |
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| 85 | /*
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| 86 | * L2,B2 system of galactic coordinates
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| 87 | *
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| 88 | * P = 192.25 RA of galactic north pole (mean B1950.0)
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| 89 | * Q = 62.6 inclination of galactic to mean B1950.0 equator
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| 90 | * R = 33 longitude of ascending node
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| 91 | *
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| 92 | * P,Q,R are degrees
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| 93 | *
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| 94 | * Equatorial to galactic rotation matrix (J2000.0), obtained by
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| 95 | * applying the standard FK4 to FK5 transformation, for zero proper
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| 96 | * motion in FK5, to the columns of the B1950 equatorial to
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| 97 | * galactic rotation matrix:
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| 98 | */
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| 99 | double rmat[3][3] = {
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| 100 | { -0.054875539726,-0.873437108010,-0.483834985808 },
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| 101 | { +0.494109453312,-0.444829589425,+0.746982251810 },
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| 102 | { -0.867666135858,-0.198076386122,+0.455983795705 }
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| 103 | };
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| 104 |
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| 105 | /* Spherical to Cartesian */
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| 106 | eraS2c( dr, dd, v1 );
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| 107 |
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| 108 | /* Equatorial to Galactic */
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| 109 | eraRxp( rmat, v1, v2 );
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| 110 |
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| 111 | /* Cartesian to spherical */
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| 112 | eraC2s( v2, dl, db );
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| 113 |
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| 114 | /* Express in conventional ranges */
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| 115 | *dl = eraAnp( *dl );
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| 116 | *db = eraAnpm( *db );
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| 117 |
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| 118 | }
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