Thank you for posting that article on optical resolution 4th_point. I could never understand why my 15-60x60 older Redfield spotting scope always looked a bit sharper at around 40x than it did up at 60x until I read your article.
I found it really interesting too!
Over the years, I came to the rough conclusion that most spotting scopes were OK up to a theoretical 2mm exit pupil or a little more. So for a 60mm, 60mm/2mm = 30 magnification (or a little less zoom), but I never really knew why. Those observations were mostly based on budget class scopes though and not high end. But even some "alpha" scopes seemed to have that characteristic too but I haven't looked at that class in several years and it sounds like the zoom eyepieces have gotten really good recently.
