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Message: <blockquote data-quote="looksharp65" data-source="post: 3639532" data-attributes="member: 83771">Thank you Ed! Feeling a bit like a bad guy when Omid invested so much headwork.Now for another tidbit from the goody bag of optics. The insight struck me that one a lot better way to achieve a laterally extended FOV would be to decenter the eyepiece's field stops laterally.Just like the prism method, the total FOV would increase at the expense of the compound FOV. However without all the other disadvantages like eye strain/headache/diplopia and seemingly reduced magnification, not to mention the compromised image quality due to chromatic aberration and the need to fine-adjust the prism base direction for IPD.Like previously mentioned, even a wide-angle binocular's FOV is about 40 degrees narrower than the human FOV, which means that an ordinary binocular's FOV represents a fraction of the human FOV. When moving the eyes within the view, the human FOV follows within the available FOV of the binocular.This is why divergent FsOV or decentered fieldstops will consume parts of the compound FOV, and that is why wide-angle binoculars, roofs and porros alike, always will be a better way to expand the FOV.//L</blockquote>