| 1 | #include "slalib.h"
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| 2 | #include "slamac.h"
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| 3 | void slaMapqk ( double rm, double dm, double pr, double pd,
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| 4 | double px, double rv, double amprms[21],
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| 5 | double *ra, double *da )
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| 6 | /*
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| 7 | ** - - - - - - - - -
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| 8 | ** s l a M a p q k
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| 9 | ** - - - - - - - - -
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| 10 | **
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| 11 | ** Quick mean to apparent place: transform a star RA,Dec from
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| 12 | ** mean place to geocentric apparent place, given the
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| 13 | ** star-independent parameters.
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| 14 | **
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| 15 | ** Use of this routine is appropriate when efficiency is important
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| 16 | ** and where many star positions, all referred to the same equator
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| 17 | ** and equinox, are to be transformed for one epoch. The
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| 18 | ** star-independent parameters can be obtained by calling the
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| 19 | ** slaMappa routine.
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| 20 | **
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| 21 | ** If the parallax and proper motions are zero the slaMapqkz
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| 22 | ** routine can be used instead.
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| 23 | **
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| 24 | ** The reference frames and timescales used are post IAU 1976.
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| 25 | **
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| 26 | ** Given:
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| 27 | ** rm,dm double mean RA,Dec (rad)
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| 28 | ** pr,pd double proper motions: RA,Dec changes per Julian year
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| 29 | ** px double parallax (arcsec)
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| 30 | ** rv double radial velocity (km/sec, +ve if receding)
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| 31 | **
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| 32 | ** amprms double[21] star-independent mean-to-apparent parameters:
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| 33 | **
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| 34 | ** (0) time interval for proper motion (Julian years)
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| 35 | ** (1-3) barycentric position of the Earth (AU)
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| 36 | ** (4-6) heliocentric direction of the Earth (unit vector)
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| 37 | ** (7) (grav rad Sun)*2/(Sun-Earth distance)
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| 38 | ** (8-10) barycentric Earth velocity in units of c
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| 39 | ** (11) sqrt(1-v**2) where v=modulus(abv)
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| 40 | ** (12-20) precession/nutation (3,3) matrix
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| 41 | **
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| 42 | ** Returned:
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| 43 | ** *ra,*da double apparent RA,Dec (rad)
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| 44 | **
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| 45 | ** References:
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| 46 | ** 1984 Astronomical Almanac, pp B39-B41.
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| 47 | ** (also Lederle & Schwan, Astron. Astrophys. 134, 1-6, 1984)
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| 48 | **
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| 49 | ** Notes:
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| 50 | **
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| 51 | ** 1) The vectors amprms(1-3) and amprms(4-6) are referred to
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| 52 | ** the mean equinox and equator of epoch eq.
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| 53 | **
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| 54 | ** 2) Strictly speaking, the routine is not valid for solar-system
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| 55 | ** sources, though the error will usually be extremely small.
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| 56 | ** However, to prevent gross errors in the case where the
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| 57 | ** position of the Sun is specified, the gravitational
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| 58 | ** deflection term is restrained within about 920 arcsec of the
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| 59 | ** centre of the Sun's disc. The term has a maximum value of
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| 60 | ** about 1.85 arcsec at this radius, and decreases to zero as
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| 61 | ** the centre of the disc is approached.
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| 62 | **
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| 63 | ** Called:
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| 64 | ** slaDcs2c spherical to Cartesian
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| 65 | ** slaDvdv dot product
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| 66 | ** slaDmxv matrix x vector
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| 67 | ** slaDcc2s Cartesian to spherical
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| 68 | ** slaDranrm normalize angle 0-2pi
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| 69 | **
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| 70 | ** Defined in slamac.h: DAS2R
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| 71 | **
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| 72 | ** Last revision: 15 January 2000
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| 73 | **
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| 74 | ** Copyright P.T.Wallace. All rights reserved.
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| 75 | */
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| 76 |
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| 77 | #define VF 0.21094502 /* Km/s to AU/year */
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| 78 |
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| 79 | {
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| 80 | int i;
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| 81 | double pmt, gr2e, ab1, eb[3], ehn[3], abv[3],
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| 82 | q[3], pxr, w, em[3], p[3], pn[3], pde, pdep1,
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| 83 | p1[3], p1dv, p2[3], p3[3];
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| 84 |
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| 85 | /* Unpack scalar and vector parameters */
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| 86 | pmt = amprms[0];
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| 87 | gr2e = amprms[7];
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| 88 | ab1 = amprms[11];
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| 89 | for ( i = 0; i < 3; i++ )
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| 90 | {
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| 91 | eb[i] = amprms[i+1];
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| 92 | ehn[i] = amprms[i+4];
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| 93 | abv[i] = amprms[i+8];
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| 94 | }
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| 95 |
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| 96 | /* Spherical to x,y,z */
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| 97 | slaDcs2c ( rm, dm, q );
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| 98 |
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| 99 | /* Space motion (radians per year) */
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| 100 | pxr = px * DAS2R;
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| 101 | w = VF * rv * pxr;
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| 102 | em[0] = (-pr * q[1]) - ( pd * cos ( rm ) * sin ( dm ) ) + ( w * q[0] );
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| 103 | em[1] = ( pr * q[0]) - ( pd * sin ( rm ) * sin ( dm ) ) + ( w * q[1] );
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| 104 | em[2] = ( pd * cos ( dm ) ) + ( w * q[2] );
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| 105 |
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| 106 | /* Geocentric direction of star (normalized) */
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| 107 | for ( i = 0; i < 3; i++ ) {
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| 108 | p[i] = q[i] + ( pmt * em[i] ) - ( pxr * eb[i] );
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| 109 | }
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| 110 | slaDvn ( p, pn, &w );
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| 111 |
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| 112 | /* Light deflection (restrained within the Sun's disc) */
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| 113 | pde = slaDvdv ( pn, ehn );
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| 114 | pdep1 = 1.0 + pde;
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| 115 | w = gr2e / gmax ( pdep1, 1.0e-5 );
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| 116 | for ( i = 0; i < 3; i++ ) {
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| 117 | p1[i] = pn[i] + ( w * ( ehn[i] - pde * pn[i] ) );
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| 118 | }
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| 119 |
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| 120 | /* Aberration (normalization omitted) */
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| 121 | p1dv = slaDvdv ( p1, abv );
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| 122 | w = 1.0 + p1dv / ( ab1 + 1.0 );
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| 123 | for ( i = 0; i < 3; i++ ) {
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| 124 | p2[i] = ab1 * p1[i] + w * abv[i];
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| 125 | }
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| 126 |
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| 127 | /* Precession and nutation */
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| 128 | slaDmxv ( (double(*)[3]) &rms[12], p2, p3 );
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| 129 |
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| 130 | /* Geocentric apparent RA,dec */
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| 131 | slaDcc2s ( p3, ra, da );
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| 132 |
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| 133 | *ra = slaDranrm ( *ra );
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| 134 | }
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