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Message: <blockquote data-quote="kabsetz" data-source="post: 1346841" data-attributes="member: 10167">Jean-Charles,Good to have you posting again.I am one of the few who, like you use "star-testing" (examining points of light with additional magnification) routinely. Doing this soon shows one that aberrations vary a lot, usually even between the two barrels of one and the same binocular. Perhaps people do not perform this test because they are daunted by the idea that one should be able to interpret it accurately enough to assign a numerical value to their finding for it to be meaningful. Although this could be done, to some extent, with a lot of experience and very careful scrutiny, for useful practical-purpose results it is not necessary. At the simplest level, one can even get some very good information by casually examining a defocused glitter point with a hand-held binocular and no booster.</blockquote>