From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 4 Mar 2015 21:21:30 -0500 Subject: Initial commit --- src/slalib/sun67.htx/node115.html | 115 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 src/slalib/sun67.htx/node115.html (limited to 'src/slalib/sun67.htx/node115.html') diff --git a/src/slalib/sun67.htx/node115.html b/src/slalib/sun67.htx/node115.html new file mode 100644 index 0000000..cee01cc --- /dev/null +++ b/src/slalib/sun67.htx/node115.html @@ -0,0 +1,115 @@ + + + + +SLA_GMST - UT to GMST + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_GMSTA - UT to GMST (extra precision) +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_GEOC - Geodetic to Geocentric +

+

+

SLA_GMST - UT to GMST +   +

+
+
ACTION: +
Conversion from universal time UT1 to Greenwich mean +sidereal time. +

CALL: +
D = sla_GMST (UT1) +

+

+
GIVEN: +
+
+ + + + + +
UT1Duniversal time (strictly UT1) expressed as +modified Julian Date (JD-2400000.5)
+

+
RETURNED: +
+
+ + + + + +
sla_GMSTDGreenwich mean sidereal time (radians)
+

+
NOTES: +
+
1. +
The IAU 1982 expression +(see page S15 of the 1984 Astronomical +Almanac) is used, but rearranged to reduce rounding errors. This + expression is always described as giving the GMST at $0^{\rm h}$UT; + in fact, it gives the difference between the + GMST and the UT, which happens to equal the GMST (modulo + 24 hours) at $0^{\rm h}$UT each day. In sla_GMST, the + entire UT is used directly as the argument for the + canonical formula, and the fractional part of the UT is + added separately; note that the factor $1.0027379\cdots$ does + not appear. +
2. +
See also the routine sla_GMSTA, which + delivers better numerical + precision by accepting the UT date and time as separate arguments. +
+
+ +next + +up + +previous +
+ Next: SLA_GMSTA - UT to GMST (extra precision) +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_GEOC - Geodetic to Geocentric +

+

+

+SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
12 October 1999
E-mail:ptw@star.rl.ac.uk +
+ + -- cgit