|
Paul,
Just a few things to consider. ..
You can increase the back focal length of the ota by repositioning the secondary mirror. If you move it towards the primary by 18mm you will get an extra 48mm of bfl. (A positioning error out of the box might explain why your bfd is different to factory specs. There is of course a practical limit to how far you can go before you experience vignetting and field aberrations .... I'm sure Bratislav could give you an idea.
Also,
I would be reluctant to use an AO at f8 without a rotator, guide star selection will be greatly impaired.
Thinking outside the box (as is my inclination) you could put the ota in a set of rotating rings and drive the entire telescope instead of just the imaging equipment. This is entirely possible, albeit non-trivial.
Last edited by clive milne; 31-05-2014 at 11:28 PM.
|