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Originally Posted by mick pinner
Steve, what do you mean similar in performance? 3050mm fl compared to 1500mm l don't think so.
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I mean for the same aperture the two types of scopes are capable of showing you similar things. One might be an f/6 or f/5, the other an f/10, but if they have the same aperture, you'll get close to the same brightness and amount of detail in DSOs, on planets and the Moon. Wrt FL the main difference there is that you might need a 20mm eyepiece with the SCT when with the Dob you need a 10-12mm for the same power. But what you see will be similar.
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Originally Posted by norm
Would a SCT be marginally dimmer compared to a dob due to the corrector plate ?  |
Marginally, but I doubt you'd notice. And the contrast might be a bit less because the central obstruction of the SCT is larger. OTOH on the Newt you have the spider. I wouldn't worry too much about it either way. But if you do, look through some scopes before buying one.
One other thing that I'm only guessing is that Newts would reach thermal equilibrium quicker because the tube is open - esp if a fan is used behind the primary mirror.