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FOV between 1.25" and 2" EP


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ok we have a hypothetical telescope with a 20mm EP, this EP gives 60x magnification and has a 60degree aFOV.

i know that for a 1.25" EP aFOV/mag - FOV, so this would be a 1degree FOV (middle ring of a telrad)...what would the 2" give?

i assume that everything is the same as the 1.25"...just more light coming through?

if it is more light coming through is it relative to the diameter (i.e. a 1.25" has a surface area of 791.7^mm and 2" has 2026.8^mm)...so has 2.56x more light coming through it??

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As far as I know the EP barrel size has no effect on the amount of light coming through. So 1.25" and 2" EP's, both 20 mm focal length and 60° aFOV would give the same view (assuming identical quality etc.) The reason for the 2" barrel size is to allow longer focal lengths and wider aFOV. With 1.25" you are limited to about 32mm and 68° aFOV.

Edited by RikM
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