From Ric in Alabama:
I shoot high power rifle matches and need a scope that is capable of seeing the mirage clearly at 300-1000 yards. The close stuff doesn't matter much. I used a Kowa 821 and 823 for 3 years. Both were excellent scopes but I didn't see much improvement in seeing the mirage under less than idea conditions with the purchase of the Kowa 823. It has their fluorite crystal lenses and I had three of the fixed focal length eyepieces, two are the newer design.
I purchase a Pentax PF-80 with the zoom and the contrast and sharpness were slightly better than my Kowa 823. I confirm this by reading newspapers taped to a fence at rather long distances. I insured that the field of view was the same on both scopes. I did notice the eye relief was less, so scope placement was important. I later purchase the fixed W20 eyepiece...WOW. I have super field of view, contrast and sharpness. The mirage is visible under some cloud cover situations when the Kowa showed nothing. Being able to see and respond to those changes allowed me to maintain high 600 yard scores when others just as capable as myself would drop points. As a high master service rifle shooter sometimes you have to experiment with different equipment and not follow the crowd. Little advantages can and do lead to wins. As a note I had to have my Kowa 823 replaced under warranty, the first had a defect, most likely caused during shipping and wasn't as sharp as my Kowa 821. The second scope was super. So even when you upgrade, look, compare, test and be honest with yourself. The higher end European scopes are sharper than my Pentax, so budget should dictate your choices.