Quote:
Originally Posted by JA
OK to answer a question like that definitively you need to provide more information: Which RASA f/2 scope and which 6" refractor are you referring to as one needs the f-ratio, image circle sizes, central obstruction size and Astrocamera phyiscal size (diameter) data to give a well considered answer?
People do and don't choose various things for all sorts of reasons; Budget. cost, complexity, performance, ease of use etc... One thing is certain in optical (science) terms is that you will lose light if you use a sensor smaller than the image circle of the optics. It's a fact. If you don't like it, or don't like to change things that's OK.
So if you have a colour APS-c cooled camera , just use that with your 90mm f/6 with an approx 0.7x focal reducer and you will be using all the light the scope has collected. If you do so you will collect more light than using multiple 1" or 4/3" sensors on 1 or 2 extra ASKAR 400mm scopes. (as already discussed).
On that basis, I might leave you to your own thoughts now.
JA
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Thank you very much for your answers and help and efforts.
Clear skies!