slaFk54z -

SYNOPSYS

PARAMETERS

double r2000

double d2000

double bepoch

double *r1950

double *d1950

double *dr1950

double *dd1950

DESCRIPTION

  Convert a J2000.0 FK5 star position to B1950.0 FK4 assuming
  zero proper motion and parallax.

  (double precision)

  This routine converts star positions from the new, IAU 1976,
  FK5, Fricke system to the old, Bessel-Newcomb, FK4 system.

Given

     r2000,d2000     double     J2000.0 FK5 RA,Dec (rad)
     bepoch          double     Besselian epoch (e.g. 1950)

Returned

     *r1950,*d1950    double    B1950.0 FK4 RA,Dec (rad) at epoch BEPOCH
     *dr1950,*dd1950  double    B1950.0 FK4 proper motions (rad/trop.yr)

Notes

  1)  The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.

  2)  Conversion from Julian epoch 2000.0 to Besselian epoch 1950.0
      only is provided for.  Conversions involving other epochs will
      require use of the appropriate precession routines before and
      after this routine is called.

  3)  Unlike in the slaFK524 routine, the FK5 proper motions, the
      parallax and the radial velocity are presumed zero.

  4)  It is the intention that FK5 should be a close approximation
      to an inertial frame, so that distant objects have zero proper
      motion;  such objects have (in general) non-zero proper motion
      in FK4, and this routine returns those fictitious proper
      motions.

  5)  The position returned by this routine is in the B1950
      reference frame but at Besselian epoch bepoch.  For
      comparison with catalogues the bepoch argument will
      frequently be 1950.0.

Called

 slaFk524, slaPm

  P.T.Wallace   Starlink   30 October 1993

SEE ALSO

• slalib.3