Les, shall we step outside and settle this like gentlemen?
I understand what you say about a 10" mirror is a 10" mirror. No argument from me there, but maybe I didn't make myself understood.
*I seen through both 'fast' and 'slow' scopes, of the same size and different. I much prefer the image of a planet through a slow scope, 8" f/6, than a fast scope 10" f4.5, both newtonians and side by side comparison, very similar focal length. The image is clearer and not as glarry in the 8". Don't even go there with collimation and optical quality! Don't! But if you must know, 8" GSO primary, 10" Parks primary.
Conversly, DSOs are better through the 10", though the sky glow is brighter than in the 8".
I don't believe it is the relative size difference of the secondaries. The percentage difference I don't think if preceivable by out eyes, except to "experienced observers". Maybe.
I think there may be a further misunderstanding of the effects of the f/ratio,
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*Well of cause you reduce the apeture with the mask, how else do you increase the effective f/ratio. That is the purpose of the mask. Yes you are reducing light gathering capability, but the planets are bright enough not to need 'light buckets' to observe well. The atmosphere is more a limiting factor to resolution than inches.
Comparing with my 17.5" f/4.5, bright planets are a better visual experience in an 8" f/6, with the same magnification. Too much light in the 17.5".
*The size of a secondary in a slow scope is smaller than that in a fast scope- you said this yourself. So what is there not to understand with a large obstruction not increasing f/ratio? It is reducing the effective diameter of the scope. The central obstruction in an SCT is huge compared to a newt. In the extreme, no way is a 10" f/10 SCT equivalent in light gathering to a 10 f/5 newt, magnification for magnification.
Now, of cause if we were able to do a like-for-like with magnification comparison between a fast scope and a slow one, both same size, we may we see the same image brightness. However, I must say that most comparisons done in the field is by swapping the same EP between scopes,
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The purpose of this thread, and my post, is to offer practical suggestions on how to improve planetary viewing with given gear.
Ta for the bits I did get 'right',
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Now, where can we share a brew?
