source: trunk/MagicSoft/slalib/amp.c@ 10075

Last change on this file since 10075 was 731, checked in by tbretz, 24 years ago
*** empty log message ***
  • Property svn:executable set to *
File size: 2.1 KB
Line 
1#include "slalib.h"
2#include "slamac.h"
3void slaAmp ( double ra, double da, double date, double eq,
4 double *rm, double *dm )
5/*
6** - - - - - - -
7** s l a A m p
8** - - - - - - -
9**
10** Convert star RA,Dec from geocentric apparent to mean place.
11**
12** The mean coordinate system is the post IAU 1976 system,
13** loosely called FK5.
14**
15** Given:
16** ra double apparent RA (radians)
17** da double apparent Dec (radians)
18** date double TDB for apparent place (JD-2400000.5)
19** eq double equinox: Julian epoch of mean place
20**
21** Returned:
22** *rm double mean RA (radians)
23** *dm double mean Dec (radians)
24**
25** References:
26** 1984 Astronomical Almanac, pp B39-B41.
27** (also Lederle & Schwan, Astron. Astrophys. 134, 1-6, 1984)
28**
29** Notes:
30**
31** 1) The distinction between the required TDB and the more
32** accessible TT is always negligible. Moreover, for all
33** but the most critical applications UTC is adequate.
34**
35** 2) The accuracy is limited by the routine slaEvp, called
36** by slaMappa, which computes the Earth positions and
37** velocities using the methods of Stumpff. The maximum
38** error is about 0.3 milliarcsecond.
39**
40** 3) Iterative techniques are used for the aberration and
41** light deflection corrections so that the routines
42** slaAmp (or slaAmpqk) and slaMap (or slaMapqk) are
43** accurate inverses; even at the edge of the Sun's disc
44** the discrepancy is only about 1 nanoarcsecond.
45**
46** 4) Where multiple apparent places are to be converted to
47** mean places, for a fixed date and equinox, it is more
48** efficient to use the slaMappa routine to compute the
49** required parameters once, followed by one call to
50** slaAmpqk per star.
51**
52** Called: slaMappa, slaAmpqk
53**
54** Last revision: 12 June 1996
55**
56** Copyright P.T.Wallace. All rights reserved.
57**
58*/
59{
60 double amprms[21]; /* Mean-to-apparent parameters */
61
62 slaMappa ( eq, date, amprms );
63 slaAmpqk ( ra, da, amprms, rm, dm );
64}
Note: See TracBrowser for help on using the repository browser.