This just seems a little odd to me. The 34 ES 68º has a 38.6mm field stop whereas the shorter focal length 30mm 70º UFF a has a 38mm field stop. I would expect the field stop of the UFF to less than 37mm. Did you notice the comparative RD between the 34 ES68 and the UFF?
Bill, I have absolutely NO FAITH, anymore, in the listed "AFOV" from ANY manufacturer. The listed AFOV is pure marketing malarkey, in my opinion. If you want to know the TFOV of an eyepiece, you MUST know the field stop, or be ready to scientifically test with the drift method. I am far too lazy to do the latter, but I can say, unequivocally, having compared the two one immediately after the other, same scope, diagonal, etc., that the APM 30mm UFF has considerably more TFOV than the ES 28mm 68º. Now, if the AFOV of the APM and ES 28mm 68º were all that mattered, the APM 30mm UFF couldn't have very much more field than the ES 28mm 68º, but when one looks at field stops ...
Pan 35 38.7mm
ES 34 68º 38.6mm
APM 30 UFF 38.0mm
ES 28 68º 31.6mm
Pan 27 30.5mm
... well, then it's a different story altogether. The APM 30 UFF should have less, but just barely less, than the ES 34mm 68º, and the same for the Pan 35. OTOH, it should have substantially MORE than the ES 28mm 68º, which is what I saw with my own eye. See this first impression last year.
To bastardize Hamlet, the field stop's the tool, wherein we'll catch conscience of the view.
Edited by CollinofAlabama, 21 October 2020 - 03:22 PM.