slaEtrms -

SYNOPSYS

PARAMETERS

double ep

double *ev

DESCRIPTION

  Compute the e-terms (elliptic component of annual aberration)
  vector.

  (double precision)

Given

     ep      double      Besselian epoch

Returned

     ev      double[3]   e-terms as (dx,dy,dz)

References

     1  Smith, C.A. et al, 1989.  "The transformation of astrometric
        catalog systems to the equinox J2000.0".  Astron.J. 97, 265.

     2  Yallop, B.D. et al, 1989.  "Transformation of mean star places
        from FK4 B1950.0 to FK5 J2000.0 using matrices in 6-space".
        Astron.J. 97, 274.

  Note the use of the J2000 aberration constant (20.49552 arcsec).
  This is a reflection of the fact that the e-terms embodied in
  existing star catalogues were computed from a variety of
  aberration constants.  Rather than adopting one of the old
  constants the latest value is used here.

  Defined in slamac.h:  DAS2R

  P.T.Wallace   Starlink   31 October 1993

SEE ALSO

• slalib.3