[time-nuts] Calculating sidereal time

[Steve Allen]

On Fri 2019-01-18T15:18:08-0600 Didier Juges hath writ:
> //-----------------------------------------------------------------------
> // Craig Haley 20/09/01
> //   30-06-04 CSH made small changes
> //   05-01-05 CSH modified to use mjd rather than converting to jd
> // Didier Juges
> //   18Jan19 converted to C.
> //-----------------------------------------------------------------------
> /* original Mathlab code:
> * mjd2000 = 51544.5;        %Modified Julian Date of Epoch J2000.0
> * int_mjd = floor(mjd);
> * frac_mjd = mjd-int_mjd;
> * Tu = (int_mjd-mjd2000)/36525.0;
> * gmst = 24110.54841+Tu.*(8640184.812866+Tu.*(0.093104-Tu*6.2e-6));
> * %add the mean sidereal time interval from midnight to time
> * gmst = mod(gmst+frac_mjd*86400*1.00273790934,86400);
> * %convert to hours
> * gmst = gmst/3600;
> */

This is the expression for use with FK5 that was codified
by Aoki et al. in
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1982A%26A...105..359A

It is required that this expression be evaluated at 0h UT,
which means that the argument in days since epoch must be half integral
+/-0.5, +/-1.5 etc.

This expression is no longer in use.  It was superseded Capitaine et al.
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003A%26A...406.1135C
in which formalism it is explicitly disavowed that earth rotation is time.
This is also far afield from the kind of time usually in this group.

--
Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
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