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Thread: Exit Pupil?

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    Default Exit Pupil?



    I want to be able to look at DSO's and asteroids and meteors, is having a higher exit pupil good for seeing those objects? I use binos so that is wut i am speaking about. Thank you all.

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    Default

    The size of the exit pupil isn't critical unless it is too big to fit into the pupil of your eye. If that happens, you waste some of the light, in effect reducing the aperture of your scope.

    The exit pupil of an eyepiece is the eyepiece focal length divided by your scope's focal ratio (f/ number). A young person's pupil is typically about 7mm in the dark. As you age, the maximum size gets smaller.

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    Default

    So it doesn't matter if my binos have a 3.2 pupil or a 4.0? Will one let me see DSO's better than the other?

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    Default

    Quote Originally Posted by planetnamek View Post
    So it doesn't matter if my binos have a 3.2 pupil or a 4.0? Will one let me see DSO's better than the other?
    No, it doesn't matter. Other things being equal (aperture, for example), both will work equally well for DSOs.

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    Default

    once the exit pupil meets the eyesize, then you start to lose light.

    7x50 binoculars are great for light gathering because the exit pupil is 7, as you get older, 8x50 are as good as you're going to get.
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