The Pentax SDUF-II is specifically made for imaging. It is extremely sharp across the field, and nicely flat in illumination. I would rate it with the best of the wide-field astrographs. At f/4, it is a little wider and a little faster than the alternatives.
* It is the easiest scope to focus manually that I have used. It has an oversized helical focuser with a Vernier scale. You can make exceptionally small yet accurate adjustments for focusing. This is of course critical for successful imaging at the fast focal ratio of f/4. It is the only scope, in fact, where I have not felt frustrated trying to focus manually. The key is the ability to make precise adjustments to focus position without guesswork because of the built-in scale marks.
* Back focus is quite long, long enough to use a motorized automated
focuser if you want to go that way. There is no problem fitting a motorized focuser, filter wheels, or other accessories into the image train.
* Image quality is extremely high.
* At 400mm, it has a very wide field of view for both film and CCD. You can take wide-field images with CCD that are normally reserved for film. The SDUF-II, like other Pentax scopes, is not readily available in the US, so they are not very easy to come by. It can be purchased from European distributors for $4,500.
This scope includes a custom made 2" adapter, 2”, 1.25” and .965 adapters, and hard case.
Asking $3,200 plus actual shipping. Can ship internationally.