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Message: <blockquote data-quote="Chosun Juan" data-source="post: 3535210" data-attributes="member: 92780">David, and herein lies the problem of an 'available ER' measurement.I could see the full Fov well enough, but due to all of those variable factors we have mentioned, alignment seemed super critical. This wasn't due to the 'available ER' being chewed up by overly proud eye cup rims. This was probably due to the really big diameter flat oculars, and my more wrap around style glasses. Some really sophisticated 3D scanning and measurement of my glasses, noggin, and proposed bin could have shown that up (similar to a body scan for buying clothes), but a simple 'available ER' figure had no chance of predicting that ....  :cat:This is why I don't put much stock in this measure - there will still be several mm of discrepancy possible. (for reference I really should start taking photographs in plan view of my glasses abutting various bin's eye cups ..... <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile    :)" loading="lazy" data-shortname=":)" />  . I seem to recall Ed posting some neat little diagrams demonstrating something similar to this somewhere in the past ....I would much prefer a tight +/-0.5mm ISO measurement of total ER.As I said earlier, this is a very important metric that needs to be preserved.I see no reason why the 'available ER' figure you desire could not be achieved in concert with that and something like a simple outline blueprint drawing of the eye cup with key dimensions included (rim standoff, rim diameter and profile, and eye cup extension travel) - surely in 2017 this is a very basic and easy thing to provide on a website? (maybe in place of yet another dead animal?! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile    :)" loading="lazy" data-shortname=":)" /> :eek!:  :gn:Things like alignment margins of error, sensitivity to CA, ease of view, and eyeroamaboutability for an individual and a particular bin are always going to be a bit of an esoteric art. An available ER figure just won't cut it. Until we can all 3D Print from our desktops, a home 3D scanner and measuring device, we are left with try it and see ....  :t:Chosun  :gh:</blockquote>

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