Re: ATM another question

[UC007@aol.com]

In a message dated 97-09-22 17:55:41 EDT, iss@pvtnetworks.net writes:

<< True enough & works fine for visual use. A question on the
 CCD list a few days ago about flat fielding problems when using
 field rotators resulted in the suggestion that one could rotate the
 entire scope to avoid the problem. Also true, *but* the axis of
 tube rotation would have to coincide with the axis of the rotator
 and be at 90 deg to the elevation axis as well, otherwise tracking errors 
 will result.
  >>
Usually, the need to rotate the tube or focuser is to accommodate the
physical limitations of visual observers. Cameras and CCDs are more tolerant
of peculiar positions.

Regards,
Bill Fries