Quote:
Originally Posted by andrew2008
I didn't use the field stop in my calcs for TFOV. Generally i just use AFOV / magnification. The mag for the 32 is only 46x
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Sorry, my bad, I must have divided by 22 for whatever reason…
Quote:
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The televue website advocates the use of the formula you used and just about every other site i've found uses the AFOV/mag. Backyard Astronomers Guide lists both but states the AFOV/mag is generally ok as Televue are about the only company that releases field stop. Will have to do some more reading on this. Thanks Steffen.
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The formula "field stop / focal length * 57.3" is the correct one (57.3 being the conversion factor between radians and degrees: 180/π). The "AFOV / mag" formula is an approximation for simple eyepiece designs and smallish AFOVs.
EDIT: You're right, not many eyepiece makers publish field stop sizes. I usually measure them myself where possible.
Cheers
Steffen.