Hi:

In addition to Jan's comments...

You say it's "properly polar aligned"...how did you do this. Unless you
have a dead-on polar alignment...not just pointing the scope forks at
Polaris, you're going to have some drift.

Peace,
Rod Mollise
Author of:_Choosing and Using a Schmidt Cassegrain Telescope_
http://members.aol.com/RMOLLISE/index.html