high magnification, exit pupil or seeing dominant factor?

[havasman]

With <1 year's experience and a 10" f4.7 scope, I'm saving for an Obsession but have a question regarding higher magnification. In my scope, 240X @ 1.1 exit pupil is often useful but 400X @ 0.6 exit pupil almost never is. I read that seeing conditions determine magnitude limits, period. The new scope I'm considering will give 345X @ 1.1 exit pupil and 576X @ 0.7 exit pupil from the same EP's as above. If seeing is the dominant limiting factor, rather than exit pupil, over usable magnification then the value of a new scope seems diminished since seeing at a given session remains constant between scopes. Can this assembly help clarify the matter, please? Thanks for your input.

[Jim Chandler]

I read that seeing conditions determine magnitude limits, period... If seeing is the dominant limiting factor, rather than exit pupil, over usable magnification then the value of a new scope seems diminished since seeing at a given session remains constant between scopes.

The key here is not absolute magnification, rather it's a function of magnification relative to aperture. 400x in a small scope is high power; in a large scope it's not. Both scopes are limited by the seeing, but that limitation translates to a higher absolute power in the larger scope.

By the way, I have to disagree with Ivan about seeing. Unless you like looking at featureless smudges, seeing is critical for galaxies and nebulae. M1 with good seeing has interesting detail; without, it's another boring blob. Same with galaxies. Good luck appreciating the subtleties of interacting galaxies with poor seeing!

Jim

[havasman]

Thank you, Jim, for your helpful input. That is what I hoped.