**ACTION:**- Convert star from geocentric apparent to mean place
(post IAU 1976). Use of this routine is appropriate when
efficiency is important and where many star positions are
all to be transformed for one epoch and equinox. The
star-independent parameters can be obtained by calling
the sla_MAPPA routine.
**CALL:**`CALL sla_AMPQK (RA, DA, AMPRMS, RM, DM)`

**GIVEN:**-

*RA,DA***D**apparent (radians) *AMPRMS***D(21)**star-independent mean-to-apparent parameters: (1) time interval for proper motion (Julian years) (2-4) barycentric position of the Earth (AU) (5-7) heliocentric direction of the Earth (unit vector) (8) (gravitational radius of Sun)(Sun-Earth distance) (9-11) **v**: barycentric Earth velocity in units of c(12) (13-21) precession/nutation matrix

**RETURNED:**-

*RM,DM***D**mean (radians)

**NOTES:**- 1.
- The accuracy is limited by the routine sla_EVP, called by sla_MAPPA, which computes the Earth position and velocity using the methods of Stumpff. The maximum error is about 0.3 milliarcsecond.
- 2.
- Iterative techniques are used for the aberration and light deflection corrections so that the routines sla_AMP (or sla_AMPQK) and sla_MAP (or sla_MAPQK) are accurate inverses; even at the edge of the Sun's disc the discrepancy is only about 1 nanoarcsecond.

**REFERENCES:**- 1.
- 1984
*Astronomical Almanac*, pp B39-B41. - 2.
- Lederle & Schwan, 1984.
*Astr.Astrophys.***134**, 1-6.

Starlink User Note 67

P. T. Wallace

12 October 1999

E-mail:ptw@star.rl.ac.uk