source: trunk/MagicSoft/slalib/rvlg.c@ 19942

Last change on this file since 19942 was 731, checked in by tbretz, 24 years ago
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1#include "slalib.h"
2#include "slamac.h"
3float slaRvlg ( float r2000, float d2000 )
4/*
5** - - - - - - - -
6** s l a R v l g
7** - - - - - - - -
8**
9** Velocity component in a given direction due to the combination
10** of the rotation of the Galaxy and the motion of the Galaxy
11** relative to the mean motion of the local group.
12**
13** (single precision)
14**
15** Given:
16** r2000,d2000 float J2000.0 mean RA,Dec (radians)
17**
18** Result:
19** Component of solar motion in direction r2000,d2000 (km/s)
20**
21** Sign convention:
22** The result is +ve when the Sun is receding from the
23** given point on the sky.
24**
25** Reference:
26** IAU trans 1976, 168, p201.
27**
28** Called:
29** slaCs2c, slaVdv
30**
31** Last revision: 15 July 1993
32**
33** Copyright P.T.Wallace. All rights reserved.
34*/
35{
36/*
37** Solar velocity due to galactic rotation and translation
38**
39** speed = 300 km/s
40**
41** apex = l2,b2 90deg, 0deg
42** = RA,dec 21 12 01.1 +48 19 47 J2000.0
43**
44** This is expressed in the form of a J2000.0 x,y,z vector:
45**
46** va(1) = x = -speed*cos(ra)*cos(dec)
47** va(2) = y = -speed*sin(ra)*cos(dec)
48** va(3) = z = -speed*sin(dec)
49*/
50 static float va[3] = { -148.23284f, 133.44888f, -224.09467f };
51 float vb[3];
52
53/* Convert given J2000 RA,dec to x,y,z */
54 slaCs2c ( r2000, d2000, vb );
55
56/* Compute dot product with solar motion vector */
57 return slaVdv ( va, vb);
58}
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