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Old 25-10-2020, 05:59 PM
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mental4astro (Alexander)

mental4astro is offline
Join Date: Jun 2008
Location: sydney, australia
Posts: 4,877
Ah, you do have other scopes! I wasn't aware. But it is an important point you make, and one that I was thinking about. I thought about bringing it up.

If one does have other scopes, say rich field short focal length scopes, then the question about going from 2000mm or 2500mm to 3000mm shouldn't be a concern. It really is only a concern if the scope's focal length begins to reach beyond 4000mm, even 5000mm. Then such a focal length needs even more specialized consideration, which you touched upon, namely where you have the scope set up. If seeing is not the best at the best of times, then such extreme focal lengths is a concern. But not 3000mm. I've seen a big cassegrain come up for sale recently with a focal length of some 7500mm - a VERY specialised scope!

If you don't have other, shorter focal length scopes, then it could be a concern. Maybe. Such long focal length scopes are not typically sought by newcomers to astro. So most people who are contemplating such long fl scopes, these people will already have an understanding of what these scopes offer and would be happy to make it their only scope.

And for photo, there are a totally different set of considerations.

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