"Rick Johnson" wrote

....
You have it on a drive platform I assume. They now make them that have
dual axis correction same as a standard equatorial mount. Not sure how
well they work.
........

Rick, et al:

Although I have no experience with imaging with an alt/az Dob I have seen
some pretty good work from those using them - or at least StellarCat
equipped Dob's. If you limit your imaging to the part of the sky with little
field rotation you can get 30 to 60 second exposures and just align them.
The StellarCat system will control the only field de-rotator that I know of
(actually it will control any stepper motor activated de-rotator), and it
will also take direct tracking input from SBIG cameras just like a GEM will.
I've seen good images with a Meade camera and Obsession 15 without using a
de-rotator, and I've seen great images from an Obsession 25 with a new UTA
that has a field de-rotator, focuser, and camera suspended in place of the
secondary mirror. In this case the owner was using an SBIG AO-7 in addition
to the guider input into the StellarCat. In his first image, when he did not
know what he was doing, he went about 30 minutes on an exposure (on a
25-inch!!!) and of course it was way overexposed - but it was accurately
tracked with nice round stars. He says that the biggest problem he has is
collimation since he can't look thru the scope and the Obsession was never
designed to hold all of that weight on the nose end.

George N