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Message: <blockquote data-quote="Troubador" data-source="post: 3320705" data-attributes="member: 109211">Hi DougI am not an optics expert Doug but I will stick my neck out here and risk a comment or two.AFAIK all bins are basically a jumble of distortions. All of them. Optical train designers make tough choices about how to balance distortion A against distortion B because if you try to eliminate distortion A while you might be successful, distortion B goes crazy. So binocular optical design is about making choices about balancing a range of distortions.Of course you are correct that these distortions are there no matter what you observe but my understanding is that point light sources set against an inky blackness can make some of these distortions so obvious that it spoils the viewing.These very same bins may satisfy most people most of the time for observing terrestrial subjects because the distortions are not obvious to most people. Go looking for them and you may be able to see them, but then you are observing the bins not using the bins for observing, which is a fascinating but quite different subject.IMHO.Lee</blockquote>