.help map Jun99 "Slalib Package" .nf SUBROUTINE slMAP (RM, DM, PR, PD, PX, RV, EQ, DATE, RA, DA) - - - - M A P - - - - Transform star RA,Dec from mean place to geocentric apparent The reference frames and timescales used are post IAU 1976. References: 1984 Astronomical Almanac, pp B39-B41. (also Lederle & Schwan, Astron. Astrophys. 134, 1-6, 1984) Given: RM,DM dp mean RA,Dec (rad) PR,PD dp proper motions: RA,Dec changes per Julian year PX dp parallax (arcsec) RV dp radial velocity (km/sec, +ve if receding) EQ dp epoch and equinox of star data (Julian) DATE dp TDB for apparent place (JD-2400000.5) Returned: RA,DA dp apparent RA,Dec (rad) Called: slMAPA star-independent parameters slMAPQ quick mean to apparent Notes: 1) EQ is the Julian epoch specifying both the reference frame and the epoch of the position - usually 2000. For positions where the epoch and equinox are different, use the routine slPM to apply proper motion corrections before using this routine. 2) The distinction between the required TDB and TT is always negligible. Moreover, for all but the most critical applications UTC is adequate. 3) The proper motions in RA are dRA/dt rather than cos(Dec)*dRA/dt. 4) This routine may be wasteful for some applications because it recomputes the Earth position/velocity and the precession/nutation matrix each time, and because it allows for parallax and proper motion. Where multiple transformations are to be carried out for one epoch, a faster method is to call the slMAPA routine once and then either the slMAPQ routine (which includes parallax and proper motion) or slMAPZ (which assumes zero parallax and proper motion). P.T.Wallace Starlink 19 January 1993 Copyright (C) 1995 Rutherford Appleton Laboratory Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. .fi .endhelp