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Old 12-09-2017, 01:42 PM
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FlashDrive (Poppy)
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FlashDrive is offline
 
Join Date: Apr 2008
Location: Bribie Island
Posts: 5,056
Quote:
Originally Posted by Merlin66 View Post
Col,
If it's 100mm f5 then the focal length is 500mm.
To get x20 the eyepiece fl needs to be 1/20 of 500 = 25mm
Cheers .... I've had a ' mental block ' today and couldn't remember ....
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