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.help mapqkz Jun99 "Slalib Package"
.nf
SUBROUTINE slMAPZ (RM, DM, AMPRMS, RA, DA)
- - - - - - -
M A P Z
- - - - - - -
Quick mean to apparent place: transform a star RA,Dec from
mean place to geocentric apparent place, given the
star-independent parameters, and assuming zero parallax
and proper motion.
Use of this routine is appropriate when efficiency is important
and where many star positions, all with parallax and proper
motion either zero or already allowed for, and 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 slMAPA routine.
The corresponding routine for the case of non-zero parallax
and proper motion is slMAPQ.
The reference frames and timescales used are post IAU 1976.
Given:
RM,DM d mean RA,Dec (rad)
AMPRMS d(21) star-independent mean-to-apparent parameters:
(1-4) not used
(5-7) heliocentric direction of the Earth (unit vector)
(8) (grav rad Sun)*2/(Sun-Earth distance)
(9-11) ABV: barycentric Earth velocity in units of c
(12) sqrt(1-v**2) where v=modulus(ABV)
(13-21) precession/nutation (3,3) matrix
Returned:
RA,DA d 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(2-4) and AMPRMS(5-7) are referred to the
mean equinox and equator of epoch EQ.
2) Strictly speaking, the routine is not valid for solar-system
sources, though the error will usually be extremely small.
However, to prevent gross errors in the case where the
position of the Sun is specified, the gravitational
deflection term is restrained within about 920 arcsec of the
centre of the Sun's disc. The term has a maximum value of
about 1.85 arcsec at this radius, and decreases to zero as
the centre of the disc is approached.
Called: slDS2C, slDVDV, slDMXV, slDC2S, slDA2P
P.T.Wallace Starlink 18 March 1999
Copyright (C) 1999 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
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.endhelp
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