Re: ATM another question

[iss@pvtnetworks.net]

Re

>IMHO the only way to rotate the focuser and maintain collimation short of a
>lot of very expensive machining of very expensive castings, is to rotate the
>whole telescope in its mounting saddle. This arrangement is non critical in
>so far as smoothness of bearings and concentricity is concerned. As long as
>the tube itself is stiff enough, the relationship between mirror, secondary
>and focuser remains unchanged. 

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.

 
Andy Saulietis / ISS Alt-Az-Fp Drive Systems
HDPE Worm Gears, Custom designs & Machine work
29 Serenity St  Mayhill NM 88339
505-687-3067 Voice
505-687-3021   Fax
e-mail: iss@pvtnetworks.net