slaMapqk -

SYNOPSYS

PARAMETERS

double rm

double dm

double pr

double pd

double px

double rv

double *amprms

double *ra

double *da

DESCRIPTION

  Quick mean to apparent place:  transform a star RA,Dec from
  mean place to geocentric apparent place, given the
  star-independent parameters.

  Use of this routine is appropriate when efficiency is important
  and where many star positions, all referred to the same equator
  and equinox, are to be transformed for one epoch.  The
  star-independent parameters can be obtained by calling the
  slaMappa routine.

  If the parallax and proper motions are zero the slaMapqkz
  routine can be used instead.

  The reference frames and timescales used are post IAU 1976.

Given

     rm,dm    double      mean RA,Dec (rad)
     pr,pd    double      proper motions:  RA,Dec changes per Julian year
     px       double      parallax (arcsec)
     rv       double      radial velocity (km/sec, +ve if receding)

       (0)      time interval for proper motion (Julian years)
       (1-3)    barycentric position of the Earth (AU)
       (4-6)    heliocentric direction of the Earth (unit vector)
       (7)      (grav rad Sun)*2/(Sun-Earth distance)
       (8-10)   barycentric Earth velocity in units of c
       (11)     sqrt(1-v2) where v=modulus(abv)
       (12-20)  precession/nutation (3,3) matrix

Returned

     *ra,*da  double      apparent RA,Dec (rad)

References

     1984 Astronomical Almanac, pp B39-B41.
     (also Lederle & Schwan, Astron. Astrophys. 134, 1-6, 1984)

Notes

    1)  The vectors amprms(1-3) and amprms(4-6) are referred to
        the mean equinox and equator of epoch eq.

    2)  Within about 300 arcsec of the centre of the Sun the
        gravitational deflection term is set to zero to avoid
        overflow.  Otherwise no account is taken of the
        impossibility of observing stars which lie behind
        the Sun.

Called

     slaDcs2c       spherical to Cartesian
     slaDvdv        dot product
     slaDmxv        matrix x vector
     slaDcc2s       Cartesian to spherical
     slaDranrm      normalize angle 0-2pi

  Defined in slamac.h:  DAS2R

  P.T.Wallace   Starlink   31 October 1993

SEE ALSO

• slalib.3