David,
> It's as per fortran slalib, so I guess that means no?
Correct - the Starlink version that is.
> If I'm interpreting
> things correctly, the equation of the equinoxes is IAU 1994 and the
> UT1-GMST relation is IAU 1982.
That'll be right.
> Keeping up with changing IAU recommendations could be a problem.
Yes.
> Presumably a supposedly general purpose thing like TimeFrame should
> ideally support a range of historical conventions as well as current
> conventions, since there will be lots of data out there which use the
> historical conventions?
There's an argument for making the 1982/1994 sidereal times the last ones
as a matter of policy, as the IAU 2000 resolutions recommend moving to
apparent RAs based on the CIO rather than the equinox.
Adding ERA to the list would give a veneer of modernity very cheaply: it's
just a linear function of UT1 and can be regarded as the new ST. No
equation of the equinoxes and, because the ERA(UT1) expression is
canonical rather than physical, won't change in the future.
Patrick Wallace
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