source: trunk/MagicSoft/slalib/galeq.c

#include "slalib.h"
#include "slamac.h"
void slaGaleq ( double dl, double db, double *dr, double *dd )
/*
**  - - - - - - - - -
**   s l a G a l e q
**  - - - - - - - - -
**
**  Transformation from IAU 1958 Galactic coordinates to
**  J2000.0 equatorial coordinates.
**
**  (double precision)
**
**  Given:
**     dl,db       double      galactic longitude and latitude l2,b2
**
**  Returned:
**     *dr,*dd     double      J2000.0 RA,dec
**
**  (all arguments are radians)
**
**  Called:
**     slaDcs2c, slaDimxv, slaDcc2s, slaDranrm, slaDrange
**
**  Note:
**     The equatorial coordinates are J2000.0.  Use the routine
**     slaGe50 if conversion to B1950.0 'FK4' coordinates is
**     required.
**
**  Reference:
**     Blaauw et al, Mon.Not.R.astron.Soc.,121,123 (1960)
**
**  Last revision:   21 September 1998
**
**  Copyright P.T.Wallace.  All rights reserved.
*/
{
   double v1[3], v2[3];

/*
**  l2,b2 system of Galactic coordinates
**
**  p = 192.25       RA of Galactic north pole (mean B1950.0)
**  q =  62.6        inclination of Galactic to mean B1950.0 equator
**  r =  33          longitude of ascending node
**
**  p,q,r are degrees
**
**  Equatorial to Galactic rotation matrix (J2000.0), obtained by
**  applying the standard FK4 to FK5 transformation, for zero proper
**  motion in FK5, to the columns of the B1950 equatorial to
**  Galactic rotation matrix:
*/
   static double rmat[3][3] =
   {
      { -0.054875539726, -0.873437108010, -0.483834985808 },
      {  0.494109453312, -0.444829589425,  0.746982251810 },
      { -0.867666135858, -0.198076386122,  0.455983795705 }
   };

/* Spherical to Cartesian */
   slaDcs2c ( dl, db, v1 );

/* Galactic to equatorial */
   slaDimxv ( rmat, v1, v2 );

/* Cartesian to spherical */
   slaDcc2s ( v2, dr, dd );

/* Express in conventional ranges */
   *dr = slaDranrm ( *dr );
   *dd = slaDrange ( *dd );
}