Is the 80mm Ed considered a "fast" scope? (1 Viewer)

This is a stupid question, I know, but I actually have been searching for the answer for about an hour now - can't get the answer! I finally got the focal length of the 80mm ED = 520. I am looking at EP's again and I know that some work better in "fast" scopes than others.

Lulubelle:

I do not know if there is an actual focal length designation for "Fast Scope"; it's a term that is most often used in reference to telescopes. I would think my PF-65 (390mm focal length) is much faster than your 80. I can say from my experience with my scope that an 8mm EP is too much magnification; but a 9mm is fine.

On the other end, any EP with a focal length longer than 17mm does not provide the minimum level of magnification that is acceptable to me in a spotting scope. I doubt that you will have any trouble with EP's down to 10mm (52x) and possible 8mm (65x). Longer focal lenght EP's such as a 30mm will only yield 17.3x and a 40mm would only yield 13x in your scope.

Pentax makes an XW in 10mm that has a pretty good reputation.

Good luck!

bearclawthedonut

I think Tele Vue is the only company that proclaims its eyepieces are designed for scopes as fast as F5. Fortunately, the PF-80ED would not be classified as a fast optic even if it operated at its full 80mm aperture. Since the aperture restriction caused by the focus mechanism turns the scope into a ~70mm optic, you should have no issues even with simple plossls. As mentioned, the high mag focal length sweet spot for an eyepiece in this scope is 10-14mm.