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Focal Length of a Mak

Started by tomrod, 09/20/2002 12:21AM
Posted 09/20/2002 12:21AM Opening Post
I have a couple Mak's and I am not quite sure how to determine the actual focal length with different configurations. As I understand it the true focal length changes when a mirror is moved to change focus.

Both of these scopes (Questar 3.5 & 7) have turrets which change focal length so I need to take many readings. I have an inspection scope that lets me measure exit pupil's accurately. I believe that if I focus the scope at infinity and then measure the exit pupil of a known eyepiece, I can calcuulate an accurate focal length of the scope.

Is this a good plan?

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