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I own a Skywatcher ED100 F9 scope. Also a number of reflectors from 6" to 16".
Resolution wise, the ED100 will give your reflector a run for it's money! The ED100, though only a doublet, made at F9 it's still very good. There are a number of losses and aberrations in reflectors that are not present in refractors. Increased aperture, while theoretically increasing resolution, needs better seeing to do so.
That flat mirror in the middle of the light path doesn't help either and knocks the T-stop down. So while a reflector has an F-ratio of F5, it's not as bright as an F5 refractor. The reflector would likely have a T-stop of 6, or more! Refractors transmit more light than reflectors which require two bounces. I would say my BD SW ED100 with focal reducer is roughly neck to neck with my 6" F5 Newtonian.
However, 4" verses 8" is still a considerable gap causing the refractor to need much longer time on the target. That's why my ED100 doesn't get much camera time lately. It can't match the 10" F4.
Give it a go though. It may surprise you. Remember to give it longer time on target to compensate.
Oh, and nice Eta Carina!
Last edited by cometcatcher; 27-04-2017 at 12:00 AM.
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