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Message: <blockquote data-quote="Mark9473" data-source="post: 3478620" data-attributes="member: 106929">You have found that the test is only qualitative and approximate, and that's what it is. I would say, if you're looking normally into the instrument, and the star is within the blur, collimation is likely to be good enough for most users.Note that vertical displacement is more critical than horizontal - our eyes have some horizontal adjustment.I realize that binoculars with a larger diopter range would give a different result, so don't take this for the ultimately accurate test. It's just an easy one that everyone can perform and that almost rules out that your eyes are playing tricks on you.</blockquote>