Double stars/nutation accuracy

Bill J. Gray Aug 12, 2001

Owen, about double-star catalog(ue)s and display: Yes, Guide 8 will
have WDS-2000 in place of the WDS-1996 that I used for Guide 7. It will
also have CCDM on it.

Stephen, I am really not too sure of the time scale for which the
nutation formulae are accurate. But I can guarantee that by the time of
a full precessional cycle of 25000-odd years, worse problems crop up.

http://www.projectpluto.com/accuracy.htm#distant

describes some of them. The nutation algorithm comes from Meeus,
and is a truncated version of the IAU theory of nutation. The source
code is available as part of the 'basic astronomical source code' at

http://www.projectpluto.com/source.htm#nutation_cpp

It may be totally off for such distant dates (though I don't know
that this is so). But you wouldn't really be able to tell, because
the maximum error that would contribute would be about an arcminute;
errors in obliquity and precession would swamp that.

-- Bill