Hi folks,

I've just posted another bug fix update at the usual site,

http://home.gwi.net/~pluto/guide8b.zip

This fixes two bugs, neither of them probably interesting to
about 99% of Guide users. If you need truly exact positional
data for stars, or for the moon in ancient times, read on.

The first bug was mentioned to me recently by Jan Manek: in
'More Info', Guide gave a slightly inaccurate result for the
Hipparcos positions of most stars (off by 8.75 years of proper
motion). That was the result of a _different_ bug that I'd fixed
earlier; fixing one bug caused this new one to occur.

Anyway, after a fair bit of puzzling, it all appears to work
properly, and when you ask Guide for 'more info' on an Hipparcos
star, the assorted positional data is correct.

The second bug was mentioned by Thomas in

http://groups.yahoo.com/group/guide-user/message/4690

involving inconsistent lunar eclipse predictions for the distant
past when using DE-406. This took still more investigation.

The problem arises because DE-406 assumes that the moon is
receding at a slightly different rate than VSOP/ELP. And if the
moon is receding at a different rate, the earth's rotation is
being slowed down at a different rate... meaning you have to adjust
Delta-T. It took me a little while to figure out how this ought
to work, but in the currently posted version, it now does. No
matter whether VSOP or DE-406 is used, you'll get the correct times.

The difference is less than a second for dates within a century
of the present, but grows quadratically with time.

-- Bill