After much deliberation, I recently purchased a new Kowa Prominar 66A scope with the TE-11WZ II zoom eyepiece. Although I am inexperienced with scopes, in my evaluation it is a well-built scope that manages to be both sturdy and lightweight. At lower magnification, colours appear vividly and images are crisp. I viewed a bald eagle about 400-500 m away and could see the wind ruffling its feathers and how pale its eyes were (paler than I expected!).
However, I've noticed that when I nudge the zoom past 35x or 40x brightness noticeably diminishes and fine details are harder to make out. I assume this is due to the decreasing size of the exit pupil relative to the higher magnification. Is this to be expected with the smaller objective lens? I imagine the 88A would outperform the 66A at this level of magnification, but at what magnification would I expect the brightness to drop off on the 88?
I know many birders choose to use fixed wide angle eyepieces, and these are often in the range of 35x, so perhaps I shouldn't complain that there is a loss of brightness/resolution when I push my zoom eyepiece beyond that number if the view at 35x is crisp and clear and beautiful. It does kind of go against the natural expectation that when one gets closer to something, one sees it better. I would be curious to hear why some prefer the fixed magnification eyepieces?
I chose the 66A for its versatility. With its smaller size, I can take it more readily on longer bird walks. With its premium glass, reviewers say it performs quite well despite its small size. However, I am fortunate enough to live on the coast, with a stellar view of the water. I can do a lot of birding just from my backyard. Would the 88 perform better in this context? With the warm weather recently, I've noticed a fair amount of atmospheric distortion when glassing over the water. Would this distortion be amplified by the bigger objective lens?
Many thanks,
DL
However, I've noticed that when I nudge the zoom past 35x or 40x brightness noticeably diminishes and fine details are harder to make out. I assume this is due to the decreasing size of the exit pupil relative to the higher magnification. Is this to be expected with the smaller objective lens? I imagine the 88A would outperform the 66A at this level of magnification, but at what magnification would I expect the brightness to drop off on the 88?
I know many birders choose to use fixed wide angle eyepieces, and these are often in the range of 35x, so perhaps I shouldn't complain that there is a loss of brightness/resolution when I push my zoom eyepiece beyond that number if the view at 35x is crisp and clear and beautiful. It does kind of go against the natural expectation that when one gets closer to something, one sees it better. I would be curious to hear why some prefer the fixed magnification eyepieces?
I chose the 66A for its versatility. With its smaller size, I can take it more readily on longer bird walks. With its premium glass, reviewers say it performs quite well despite its small size. However, I am fortunate enough to live on the coast, with a stellar view of the water. I can do a lot of birding just from my backyard. Would the 88 perform better in this context? With the warm weather recently, I've noticed a fair amount of atmospheric distortion when glassing over the water. Would this distortion be amplified by the bigger objective lens?
Many thanks,
DL