[AZ-Observing] Re: Jennifer's confluence info please

Seeing as how all of these positions are within the boundaries of the two
strings of stars I am satisfied.

Steve Coe


-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Brian Skiff
Sent: Friday, July 25, 2008 5:18 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Jennifer's confluence info please

>>  Possibly due to the Epoch?....
>>  epoch of the date vs. J2000....
>>  Object position for epoch J2000.0....


     Finicky astromamers will want to note that here (and just about
everywhere else) when the word "epoch" is used, "equinox" is meant.
Many software packages and books have this wrong, and indeed
most professional astronomers use the words interchangeably (and
thus incorrectly).
     Epoch is only necessary for things that are moving with
respect to a nominally fixed reference frame, such as a star with
large proper-motion that is in a different place in 1942 (say)
than it is in 2008.  What most folks talk about is precession
of the coordinate system itself, as in precession of the equinoxes,
and that's what we're talking about here, i.e. the equinox for
which the coordinate system applies.
     I wonder that in order to have something relatively definite
to hang your hat on in terms of the position, one might adopt the
position of the triple star h 594, something like 18 13 46 -18 48.6 (J2000).


\Brian
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