Thanks David. That is an excellent straightforward method, though it wouldn't directly work for me since I'm blind in one eye (grin). Think I understand the principle of the procedure though-- Use one eye direct-viewing to match the unfocused illuminated field stop seen thru the other eye, and use the ruler and trig to calc the subtended angle.

If I REALLY want to measure it, could probably kludge up some half-silvered mirror or prism gadget that would give the same result with one eye...

Apologies, my original question was probably drifting the thread too much. Psych perceptions are so dependent on set and setting, and I'm willing to believe that a Q70 AFOV really is in the ballpark of 70 degrees. If it were substantially greater, then they would likely have taken marketing advantage by naming it a Q80 or Q90 (grin).

I love science, and make a living on technology, but my reason for looking thru scopes is to see the pretty pictures. Since the 38mm Q70 seems to make a prettier, more immersive picture than some other eyepieces which have similar or bigger published AFOV-- I was just curious what eyepiece specs one would look for, since the AFOV spec doesn't seem to be the one that matters. If that makes sense. I don't know much about it.

Maybe there is something similar about the hyperions which makes them popular-- Some subjective pleasant immersive experience that isn't described by the AFOV alone. I've not looked thru hyperions, but there must be something special that makes them more gratifying than other budget eyepieces which have similar AFOV?

There are quite a few EP lines with 65 degree or better AFOV, but some of them just feel like you are seeing a wide view thru a tiny peephole.

Thanks

jcjr