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
69
70
71
72
73
74
75
76
|
.help mapqk Jun99 "Slalib Package"
.nf
SUBROUTINE slMAPQ (RM, DM, PR, PD, PX, RV, AMPRMS, RA, DA)
- - - - - -
M A P Q
- - - - - -
Quick mean to apparent place: transform a star RA,Dec from
mean place to geocentric apparent place, given the
star-independent parameters.
Use of this routine is appropriate when efficiency is important
and where many star positions, 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.
If the parallax and proper motions are zero the slMAPZ
routine can be used instead.
The reference frames and timescales used are post IAU 1976.
Given:
RM,DM d mean RA,Dec (rad)
PR,PD d proper motions: RA,Dec changes per Julian year
PX d parallax (arcsec)
RV d radial velocity (km/sec, +ve if receding)
AMPRMS d(21) star-independent mean-to-apparent parameters:
(1) time interval for proper motion (Julian years)
(2-4) barycentric position of the Earth (AU)
(5-7) heliocentric direction of the Earth (unit vector)
(8) (grav rad Sun)*2/(Sun-Earth distance)
(9-11) 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 spherical to Cartesian
slDVDV dot product
slDMXV matrix x vector
slDC2S Cartesian to spherical
slDA2P normalize angle 0-2Pi
P.T.Wallace Starlink 23 August 1996
Copyright (C) 1996 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
.fi
.endhelp
|
