Results 1 to 3 of 3

Thread: high magnification, exit pupil or seeing dominant factor?

  1. #1
    Member
    Join Date
    Apr 2014
    Location
    Dallas, Texas
    Posts
    5

    high magnification, exit pupil or seeing dominant factor?

    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.

  2. #2
    Big Jim Jim Chandler's Avatar
    Join Date
    Feb 2012
    Location
    Fort Davis, Texas
    Posts
    91
    Quote Originally Posted by havasman View Post
    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

  3. #3
    Member
    Join Date
    Apr 2014
    Location
    Dallas, Texas
    Posts
    5
    Thank you, Jim, for your helpful input. That is what I hoped.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •