On Mon, 26 Dec 2005 01:56:18 -0500, Davoud wrote:

Now, however, I am in the process of installing a GEM. A GEM ought to
be in the center of the dome, I am told. Moving he pier -- and the
1,600 lb. concrete footer it rests on -- is not an option. Rebuilding
the zerbatory around the pier is an option, but not one to be desired
or taken lightly. What kinds of problems, if any, am I likely to
encounter in tracking and fine guiding with the GEM improperly located?

The only real trouble you would have is when the telescope or
counterweight bumps into the dome. I think you would minimize the
diameter of the dome when the intersection of the polar and
declination axes is near the center of the dome. This is not
necessarily at the center of the pier. The offsets for your two
mounts are likely to be similar.

Even research observatories can have trouble with this. The staff at
one facility was chagrined to discover their new pier was too short
for their new telescope when it was all assembled.