What am I missing re Exit Pupil size?

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What am I missing re Exit Pupil size?

Postby 47Tuc » Wed Nov 03, 2010 10:00 am

As you can see from my other post, there are some things about the September Group Test which I don't understand. The Hyperion 3.5mm is criticised for having a small exit pupil, whereas the Orion 3.7mm is praised for having "a sensibly wide exit pupil". I thought that [i]in the same telescope[/i] the only thing determining exit pupil was the EP focal length. Since the focal lengths of the two EPs are very similar I would have expected the exit pupils to be very similar. What am I missing?
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RE: What am I missing re Exit Pupil size?

Postby brianb » Wed Nov 03, 2010 11:40 am

Dunno ... your logic is right. In any case 3.7mm is far too short for any scope except a f/4 Newtonian, even then it's an extreme high power.

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