blob: 7e58aec95f79446c379fe24c22037edbbd635031 (
plain) (
blame)
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
|
.help gmst Jun99 "Slalib Package"
.nf
DOUBLE PRECISION FUNCTION slGMST (UT1)
- - - - -
G M S T
- - - - -
Conversion from universal time to sidereal time (double precision)
Given:
UT1 dp universal time (strictly UT1) expressed as
modified Julian Date (JD-2400000.5)
The result is the Greenwich mean sidereal time (double
precision, radians).
The IAU 1982 expression (see page S15 of 1984 Astronomical
Almanac) is used, but rearranged to reduce rounding errors.
This expression is always described as giving the GMST at
0 hours UT. In fact, it gives the difference between the
GMST and the UT, which happens to equal the GMST (modulo
24 hours) at 0 hours UT each day. In this routine, the
entire UT is used directly as the argument for the
standard formula, and the fractional part of the UT is
added separately; note that the factor 1.0027379... does
not appear.
See also the routine slGMSA, which delivers better numerical
precision by accepting the UT date and time as separate arguments.
Called: slDA2P
P.T.Wallace Starlink 14 September 1995
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
.fi
.endhelp
|
