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Message: <blockquote data-quote="pompadour" data-source="post: 2756795" data-attributes="member: 104665">Dalat, I did think the same way - you don't see more birds (or stars). Maybe I've been a bit carried away by praise in BF and elsewhere for a large apparent field of view, relevant ~ 60° for terrestrial use: the "walk-in" effect, and more relaxed viewing, which would matter to most people. (Haven't myself been able to see such a field of view yet since I learnt this.) In another BF thread/s these days they say for astronomy the FOV in a bin can also be too much and disturbing - I guess "space-walk in" is not so natural.Holger, thanks. I now see the relevance of directly multiplying the angle - took a bit of time! By "here" in "not mentioned much here" I meant not this thread but BF, and brought up less than I would expect, as the paragraph above might explain. I'd guess - excuse my ignorance - that Vr is pretty difficult to calculate effectively for the optical system of a bin. If that is correct it may be simpler to measure a. Then if Vr is necessray the formula gives it. This assumes A is relatively easy to obtain (by measuring if not calculating).David, I've been wondering how Holger feels when he sees queries in BF he has answered in his book just published. Does one say, "Actually, I've written a book, where I attempt to address such things. If you do read my humble work, this is mentioned on page abc-def" or "This is dealt with in my book. Please see page ghi" or "Read my * book!" But gracefully he again addresses the issue.</blockquote>

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