| 1 | #include "slalib.h"
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| 2 | #include "slamac.h"
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| 3 | void slaGe50 ( double dl, double db, double *dr, double *dd )
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| 4 | /*
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| 5 | ** - - - - - - - -
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| 6 | ** s l a G e 5 0
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| 7 | ** - - - - - - - -
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| 8 | **
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| 9 | ** Transformation from IAU 1958 Galactic coordinates to
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| 10 | ** B1950.0 'FK4' equatorial coordinates.
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| 11 | **
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| 12 | ** (double precision)
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| 13 | **
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| 14 | ** Given:
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| 15 | ** dl,db double Galactic longitude and latitude l2,b2
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| 16 | **
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| 17 | ** Returned:
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| 18 | ** *dr,*dd double B1950.0 'FK4' RA,Dec
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| 19 | **
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| 20 | ** (all arguments are radians)
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| 21 | **
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| 22 | ** Called:
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| 23 | ** slaDcs2c, slaDimxv, slaDcc2s, slaAddet, slaDranrm, slaDrange
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| 24 | **
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| 25 | ** Note:
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| 26 | ** The equatorial coordinates are B1950.0 'FK4'. Use the
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| 27 | ** routine slaGaleq if conversion to J2000.0 coordinates
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| 28 | ** is required.
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| 29 | **
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| 30 | ** Reference:
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| 31 | ** Blaauw et al, Mon.Not.R.astron.Soc.,121,123 (1960)
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| 32 | **
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| 33 | ** Last revision: 8 December 1993
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| 34 | **
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| 35 | ** Copyright P.T.Wallace. All rights reserved.
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| 36 | */
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| 37 | {
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| 38 | double v1[3], v2[3], r, d, re, de;
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| 39 | /*
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| 40 | ** l2,b2 system of Galactic coordinates
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| 41 | **
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| 42 | ** p = 192.25 RA of Galactic north pole (mean B1950.0)
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| 43 | ** q = 62.6 inclination of Galactic to mean B1950.0 equator
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| 44 | ** r = 33 longitude of ascending node
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| 45 | **
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| 46 | ** p,q,r are degrees
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| 47 | **
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| 48 | ** Equatorial to Galactic rotation matrix
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| 49 | **
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| 50 | ** The Euler angles are p, q, 90-r, about the z then y then
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| 51 | ** z axes.
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| 52 | **
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| 53 | ** +cp.cq.sr-sp.cr +sp.cq.sr+cp.cr -sq.sr
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| 54 | **
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| 55 | ** -cp.cq.cr-sp.sr -sp.cq.cr+cp.sr +sq.cr
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| 56 | **
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| 57 | ** +cp.sq +sp.sq +cq
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| 58 | */
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| 59 | static double rmat[3][3] =
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| 60 | {
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| 61 | { -0.066988739415, -0.872755765852, -0.483538914632 },
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| 62 | { 0.492728466075, -0.450346958020, 0.744584633283 },
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| 63 | { -0.867600811151, -0.188374601723, 0.460199784784 }
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| 64 | };
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| 65 |
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| 66 |
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| 67 | /* Spherical to Cartesian */
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| 68 | slaDcs2c ( dl, db, v1 );
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| 69 |
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| 70 | /* Rotate to mean B1950.0 */
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| 71 | slaDimxv ( rmat, v1, v2 );
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| 72 |
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| 73 | /* Cartesian to spherical */
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| 74 | slaDcc2s ( v2, &r, &d );
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| 75 |
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| 76 | /* Introduce e-terms */
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| 77 | slaAddet ( r, d, 1950.0, &re, &de );
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| 78 |
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| 79 | /* Express in conventional ranges */
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| 80 | *dr = slaDranrm ( re );
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| 81 | *dd = slaDrange ( de );
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| 82 | }
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