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slalib/eg50.f

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+      SUBROUTINE sla_EG50 (DR, DD, DL, DB)
+*+
+*     - - - - -
+*      E G 5 0
+*     - - - - -
+*
+*  Transformation from B1950.0 'FK4' equatorial coordinates to
+*  IAU 1958 galactic coordinates (double precision)
+*
+*  Given:
+*     DR,DD       dp       B1950.0 'FK4' RA,Dec
+*
+*  Returned:
+*     DL,DB       dp       galactic longitude and latitude L2,B2
+*
+*  (all arguments are radians)
+*
+*  Called:
+*     sla_DCS2C, sla_DMXV, sla_DCC2S, sla_SUBET, sla_DRANRM, sla_DRANGE
+*
+*  Note:
+*     The equatorial coordinates are B1950.0 'FK4'.  Use the
+*     routine sla_EQGAL if conversion from J2000.0 coordinates
+*     is required.
+*
+*  Reference:
+*     Blaauw et al, Mon.Not.R.Astron.Soc.,121,123 (1960)
+*
+*  P.T.Wallace   Starlink   5 September 1993
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*
+*  License:
+*    This program is free software; you can redistribute it and/or modify
+*    it under the terms of the GNU General Public License as published by
+*    the Free Software Foundation; either version 2 of the License, or
+*    (at your option) any later version.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU General Public License for more details.
+*
+*    You should have received a copy of the GNU General Public License
+*    along with this program (see SLA_CONDITIONS); if not, write to the 
+*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION DR,DD,DL,DB
+
+      DOUBLE PRECISION sla_DRANRM,sla_DRANGE
+
+      DOUBLE PRECISION V1(3),V2(3),R,D
+
+*
+*  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
+*
+*  The Euler angles are P, Q, 90-R, about the z then y then
+*  z axes.
+*
+*         +CP.CQ.SR-SP.CR     +SP.CQ.SR+CP.CR     -SQ.SR
+*
+*         -CP.CQ.CR-SP.SR     -SP.CQ.CR+CP.SR     +SQ.CR
+*
+*         +CP.SQ              +SP.SQ              +CQ
+*
+
+      DOUBLE PRECISION RMAT(3,3)
+      DATA RMAT(1,1),RMAT(1,2),RMAT(1,3),
+     :     RMAT(2,1),RMAT(2,2),RMAT(2,3),
+     :     RMAT(3,1),RMAT(3,2),RMAT(3,3) /
+     : -0.066988739415D0,-0.872755765852D0,-0.483538914632D0,
+     : +0.492728466075D0,-0.450346958020D0,+0.744584633283D0,
+     : -0.867600811151D0,-0.188374601723D0,+0.460199784784D0 /
+
+
+
+*  Remove E-terms
+      CALL sla_SUBET(DR,DD,1950D0,R,D)
+
+*  Spherical to Cartesian
+      CALL sla_DCS2C(R,D,V1)
+
+*  Rotate to galactic
+      CALL sla_DMXV(RMAT,V1,V2)
+
+*  Cartesian to spherical
+      CALL sla_DCC2S(V2,DL,DB)
+
+*  Express angles in conventional ranges
+      DL=sla_DRANRM(DL)
+      DB=sla_DRANGE(DB)
+
+      END