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ED80 vs 8" reflector
Following on from a recent post in Beginners' Equipment...
I took some (very rough & kinda terrible) shots of the Moon, Mars and Omega Centauri tonight with both a little 80/600mm refractor and a 200/1000mm Newtonian reflector. Same exact camera & camera settings for each target. I switched OTAs between targets (meaning I took a shot, changed OTA, took the same shot, changed OTA, took second shot, changed OTA etc).
The ED80 had a 0.85 flattener on it so it was essentially f/6.4. The reflector is f/5. This SHOULD mean that the newt would be significantly brighter, like two thirds of a stop... but it clearly isn't.
Anyone have any suggestions why this should be? The secondary blocks a little of the light, but nowhere near 30% of it. Is a large part of the light "missed" by the secondary? Inherent vignetting by newts? Loss from the two mirrors? I just don't understand these results, it's weirding me out.
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