Computation of GAST, GMST, and ERA
2008-10-08T12:05:00Z
Computation of Greenwich Apparent Sidereal Time, Greenwich
Mean Sidereal Time, and the Earth Rotation Angle
/apfs/res/apfs_new/catquery/form
2000IAUJD...2E...5W
Apparent Places for Fundamental Stars
`_ or the
`web page of the IERS `_.
To compute the current values, leave the form empty. Otherwise,
enter a
`date expression <\internallink{/static/help_vizier.shtml#dates}>`_
(for UT1; only a subset of the available operators is supported)
and an interval (in seconds) for how often a date should
be computed.
Examples:
* ``2008-10-04T10:30:23`` gets you the values for that date
* ``2008-10-04 .. 2008-10-05`` gets you values for the entire
fourth of october.
* ``2008-10-04T10:30:23 .. 2008-10-05T10:30:23`` gets you values
between the two dates every interval seconds.
* ``2008-10-04T10:30:23 +/- 1`` gets you values for one day before
and after the given date.
]]>
`_
where also a useful glossary can be found.
For detailed information we recommend the printed version of the
Astronomical Almanac, or the `Astronomical Almanac Online `_.
GAST and GMST are
consistent with IAU 2006 precession.
Software Routines from the IAU SOFA Collection were used. Copyright ©
International Astronomical Union Standards of Fundamental Astronomy
(http://www.iausofa.org); actually, we are using ERFA in the meantime,
but SOFA credit is still due.
]]>
astrometry
geodesics
No longer
using a C wrapper around SOFA but instead going for ERFA
through astropy. We have confirmed that results are identical
up to the precision we give.
We
now actually pass TT to the SOFA routines where
required rather than approximate it by
UT1 as before. This will affect the results given
here only in rare cases, and even then only by changing
the last figure due to rounding.
ut1,gmst,gast,era
```
datetime.date.today().year+5:
targetTable.addMeta("_warning", "The change in the"
" Earth's rotation rate affects these results. Since"
" these results lie far in the future and predictions"
" of the rotation may be incorrect, these results may"
" be slightly inaccurate.")
]]>
```

times_series
q/form
```
self.assertHasStrings("Greenwich Mean Sidereal",
"12 24 29.3052", "+306 20 18.341", "04 27 07.6839")
```

q/form
```
self.assertHasStrings("wirres Zeug", "Invalid date expression (at 0)")
```

/apfs/times/q/form
```
self.assertHasStrings("ut1,gmst,gast,era\r\n",
"2020-01-02T08:05:20,222.77298995121694,"
"222.76876933683172,222.51671035020607")
```

/apfs/times/q/api
```
rows = self.getVOTableRows()
self.assertEqual(rows[0]["ut1"].day, 1)
self.assertAlmostEqual(rows[3]["gmst"], 325.73783918610945)
self.assertAlmostEqual(rows[4]["gast"], 340.7746968714495)
self.assertAlmostEqual(rows[5]["era"], 355.5637191110078)
```