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To get back to being serious any system at F3 will present problems that are very minor at slower F ratios.
OAG's are useless as the steeply convergent light beams will interact with any prism or even a coherent light pipe edges due to diffraction and leave scatter all over your image. Dual chip cameras are next to useless for guiding behind 3nm filters.
Focus is very terse so temperature control of the whole optical train is vital.
Sensor alignment is a nightmare as the slightest differential flexure will be readily apparent in every exposure that is longer than a few tens of seconds.
The only thing going for a 200mm diameter optic at F3 is speed. If all the problems can be minimised it will be worth it.
I may look a bit crazy by how I approached these very real problems. I think I am almost there.
Do not be discouraged, as it all needs a totally new mindset.
All the 'rules' of the past are simply myth!
Bert
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