Quote:
Originally Posted by ballaratdragons
BUT, on the other hand, if you are a Planetary observer, the 8" blew the 12" away on Planetary stuff. Probably due to the difference in f/ratio. The 12" is f5, whereas the 8" is f6.
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I'd have to disagree with Ken on this. As I do own both scopes I can say with absolute certainty that in good seeing the 12" blows away the 8" on planets, even more so than it does on DSOs.
BUT the 12" needs more time to come to thermal equilibrium and before it does the views are disappointing. But once both scopes are properly cooled the amount of detail seen through the 12" is astonishing. E.g., on the surface of Jupiter you see a lot more intricate detail that is not visible in the 8" no matter what the conditions/power/eyepiece. It is something like going from watching VHS tapes on an old tellie to DVD on a high-res display.
I have three 80mm fans on my 12" (will be replaced with a single 120mm soon) and usually it still takes 3-4 times as long to cool down properly (20-30 minutes) than the 8" (5-7 min) with a single 90mm fan.
Other thing to consider is collimation which is more critical with the 12". It goes out more easily and the springs supplied by GSO are way too weak for the weight of the mirror. They sag badly, so you need to either replace them or use the locking screws in conj with the tilt adjust screws in a push-pull arrangement, which is what I do; a little bit of a pain but works for me. If collimation is not spot you will not benefit from the higher resolution of the larger aperture.