| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * palSubet
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| 5 |
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| 6 | * Purpose:
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| 7 | * Remove the E-terms from a pre IAU 1976 catalogue RA,Dec
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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 palSubet ( double rc, double dc, double eq,
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| 17 | * double *rm, double *dm );
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| 18 |
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| 19 | * Arguments:
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| 20 | * rc = double (Given)
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| 21 | * RA with E-terms included (radians)
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| 22 | * dc = double (Given)
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| 23 | * Dec with E-terms included (radians)
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| 24 | * eq = double (Given)
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| 25 | * Besselian epoch of mean equator and equinox
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| 26 | * rm = double * (Returned)
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| 27 | * RA without E-terms (radians)
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| 28 | * dm = double * (Returned)
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| 29 | * Dec without E-terms (radians)
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| 30 |
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| 31 | * Description:
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| 32 | * Remove the E-terms (elliptic component of annual aberration)
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| 33 | * from a pre IAU 1976 catalogue RA,Dec to give a mean place.
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| 34 |
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| 35 | * Authors:
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| 36 | * PTW: Pat Wallace (STFC)
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| 37 | * TIMJ: Tim Jenness (JAC, Hawaii)
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| 38 | * {enter_new_authors_here}
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| 39 |
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| 40 | * Notes:
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| 41 | * Most star positions from pre-1984 optical catalogues (or
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| 42 | * derived from astrometry using such stars) embody the
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| 43 | * E-terms. This routine converts such a position to a
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| 44 | * formal mean place (allowing, for example, comparison with a
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| 45 | * pulsar timing position).
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| 46 |
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| 47 | * See Also:
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| 48 | * Explanatory Supplement to the Astronomical Ephemeris,
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| 49 | * section 2D, page 48.
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| 50 |
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| 51 | * History:
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| 52 | * 2012-02-12(TIMJ):
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| 53 | * Initial version with documentation taken from Fortran SLA
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| 54 | * Adapted with permission from the Fortran SLALIB library.
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| 55 | * {enter_further_changes_here}
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| 56 |
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| 57 | * Copyright:
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| 58 | * Copyright (C) 1995 Rutherford Appleton Laboratory
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| 59 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 60 | * All Rights Reserved.
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| 61 |
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| 62 | * Licence:
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| 63 | * This program is free software: you can redistribute it and/or
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| 64 | * modify it under the terms of the GNU Lesser General Public
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| 65 | * License as published by the Free Software Foundation, either
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| 66 | * version 3 of the License, or (at your option) any later
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| 67 | * version.
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| 68 | *
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| 69 | * This program is distributed in the hope that it will be useful,
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| 70 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 71 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 72 | * GNU Lesser General Public License for more details.
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| 73 | *
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| 74 | * You should have received a copy of the GNU Lesser General
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| 75 | * License along with this program. If not, see
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| 76 | * <http://www.gnu.org/licenses/>.
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| 77 |
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| 78 | * Bugs:
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| 79 | * {note_any_bugs_here}
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| 80 | *-
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| 81 | */
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| 82 |
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| 83 | #include "pal.h"
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| 84 | #include "pal1sofa.h"
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| 85 |
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| 86 | void palSubet ( double rc, double dc, double eq, double *rm, double *dm ) {
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| 87 | double a[3]; /* The E-terms */
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| 88 | double v[3];
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| 89 | double f;
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| 90 | int i;
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| 91 |
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| 92 | /* Note the preference for IAU routines */
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| 93 |
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| 94 | /* Retrieve the E-terms */
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| 95 | palEtrms( eq, a );
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| 96 |
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| 97 | /* Spherical to Cartesian */
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| 98 | eraS2c( rc, dc, v );
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| 99 |
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| 100 | /* Include the E-terms */
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| 101 | f = 1.0 + eraPdp( v, a );
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| 102 | for (i=0; i<3; i++) {
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| 103 | v[i] = f*v[i] - a[i];
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| 104 | }
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| 105 |
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| 106 | /* Cartesian to spherical */
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| 107 | eraC2s( v, rm, dm );
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| 108 |
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| 109 | /* Bring RA into conventional range */
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| 110 | *rm = eraAnp( *rm );
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| 111 |
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| 112 | }
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