Optical Differences in 20-60x vs. Fixed Magnification (1 Viewer)

Hi All,

I currently own a Fieldscope III ED AN with a new 20-60x zoom lens. I currently use the lens in a 20-30x configuration due to decreasing light levels as magnification increases (smaller EPD).

I was contemplating changing to a 24x or a 30xWA lens and I was wondering if there was any optical reason to do so. Does the newer generation zoom perform as well at the lower magnification settings as a fixed mag lens or can some extra clarity/contrast be gained by going to a fixed mag?

Thanks to all for the insight.

Rgds,

Steffan

Steffan,

To my eyes and scrutiny, the Nikon 20-60 MC II zoom is actually a tiny bit brighter and has slightly higher contrast than the 24x Wide MC, and is certainly not any less sharp. I tried both in an ED 82 A, and ended up preferring the zoom for both its flexibility and what to my eyes was a better center field image. The field width difference is dramatic, though, so if you truly feel you don't wish to go above 30x, the 30/38x Wide MC is very nice. It also gives better edge resolution than the 30x Wide.

General consensus has thus far held fixed-magnification eyepieces to be superior in most every respect, but with the recent crop of top zooms that seems no longer to be true. Modern zoom designs are so sharp throughout their range that the softening you see at high magnifications is entirely due to the limits of the scope, which become more and more visible as you crank up the magnification. Also, modern multicoatings together with the fact that well-corrected wideangles now have just as many or sometimes even more glass-to-air surfaces than corresponding zooms has led to brightness differences being barely perceptible at most.

Hope this helps.

Kimmo

Kimmo,

Thanks for the excellent information (as always).

I really like the Fieldscope III ED, as it is a nice, tough, compact little scope that seems to provide some pretty nice views.

My only complaint is that it can't change the laws of Physics for me. As I approach 50-60x with a 60mm objective, the exit pupil diameter approaches 1 mm, which is awfully small and therefore, awfully dim.

I find myself mostly in the 20-30x range, as I get a bright, sharp view using those magnifications. As a matter of fact, I spend so much time there that I just ordered a 30x WA MC from Eagle Optics.

Thanks again for your help and advice. :clap:

Rgds,

Steffan