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.help amp Jun99 "Slalib Package"
.nf
SUBROUTINE slAMP (RA, DA, DATE, EQ, RM, DM)
- - - -
A M P
- - - -
Convert star RA,Dec from geocentric apparent to mean place
The mean coordinate system is the post IAU 1976 system,
loosely called FK5.
Given:
RA d apparent RA (radians)
DA d apparent Dec (radians)
DATE d TDB for apparent place (JD-2400000.5)
EQ d equinox: Julian epoch of mean place
Returned:
RM d mean RA (radians)
DM d mean Dec (radians)
References:
1984 Astronomical Almanac, pp B39-B41.
(also Lederle & Schwan, Astron. Astrophys. 134,
1-6, 1984)
Notes:
1) The distinction between the required TDB and TT is
always negligible. Moreover, for all but the most
critical applications UTC is adequate.
2) The accuracy is limited by the routine slEVP, called
by slMAPA, which computes the Earth position and
velocity using the methods of Stumpff. The maximum
error is about 0.3 milliarcsecond.
3) Iterative techniques are used for the aberration and
light deflection corrections so that the routines
slAMP (or slAMPQ) and slMAP (or slMAPQ) are
accurate inverses; even at the edge of the Sun's disc
the discrepancy is only about 1 nanoarcsecond.
4) Where multiple apparent places are to be converted to
mean places, for a fixed date and equinox, it is more
efficient to use the slMAPA routine to compute the
required parameters once, followed by one call to
slAMPQ per star.
Called: slMAPA, slAMPQ
P.T.Wallace Starlink 19 January 1993
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
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