Computation of GAST, GMST, and ERA 2008-10-08T12:05:00Z 100 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)