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Get The 32MM

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Posted by Bob Sal on February 28, 2002 20:37:16 UTC

Here's why. Your scope is an f/4.8. Let do some arithmatic. To get the exit pupil for a telescope/eyepiece combination divide the focal length of the eyepiece by the telescope.
40 / 4.8 = 8.3. Now the average dark adapted eye has an exit pupil of around 7MM. So with a 40MM eyepiece your eye will not be able to take in all the light from the eyepiece. It's like using a smaller telescope. Now a 32MM eyepiece,
32 / 4.8 = 6.6. Now you have a better combination and can see all the light your scope delivers. It makes a difference. I can see the difference on my sons 80MM f/5 scope. The 40MM eyepiece looks dull compaired to the 32MM. It's OK if you want to use it as sort of a finder eyepiece, but if it's going to be a main eyepiece, go for the 32MM.
That's it;
BOB SAL

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