Quote:
Originally Posted by clive milne
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.
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Now that is something I had not considered. I am 1mm different from specs, but could move back 5mm.
Not worried about the AO issue as the guide camera is in the filter wheel and as yet not seen an instance where it does not find a guide star. So a rotator is just a luxury.
On another matter today I bought a flattener (see link below). Cheapish and large diameter which is what I wanted.
http://www.teleskop-express.de/shop/...=6972#ebericht
Now to get it and then I can work out the relevant backfocus and adapters.