1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
SUBROUTINE sla_AMP (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 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.
*
* 3) 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.
*
* 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 sla_MAPPA routine to compute the
* required parameters once, followed by one call to
* sla_AMPQK per star.
*
* Called: sla_MAPPA, sla_AMPQK
*
* P.T.Wallace Starlink 19 January 1993
*
* Copyright (C) 1995 Rutherford Appleton Laboratory
*-
IMPLICIT NONE
DOUBLE PRECISION RA,DA,DATE,EQ,RM,DM
DOUBLE PRECISION AMPRMS(21)
CALL sla_MAPPA(EQ,DATE,AMPRMS)
CALL sla_AMPQK(RA,DA,AMPRMS,RM,DM)
END
|
