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Well funny this should come up. I have a 10" f5 dob and I cannot find the optimum UWA eyepiece. You see My eyes are not young and a maximum exit pupil of 6mm would be best (less better still), But in a 2" barrel, The best field stop I might get is only 48mm which woulds allow 2.2 degrees of TFOV. My maths says a 30mm lens would be 1250/30=41.67 magnification. As AFOV=MagXTFOV then AFOV = 41.67X2.2 = 92 degrees. This does not really come close to the 31mm Nagler, and both it and the Moonfish have restrictive field stops - The Nagler according to reviews noticeably so. Really an exit pupil of 5mm would be better so lens is 25mm, mag is 1250/25 = X50, and AFOV = 50X2.2=110 degrees. I would settle for a 28mm with a 98 degree AFOV which will give me the same 2.2 TFOV and a 5.6mm exit pupil. I am sure this would be possible!. Surely Televue should make this a priority. Just keep an eye on the field stop thanks. Those with 12" dobs would have to shift for themselves....
cheers!
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