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Message: <blockquote data-quote="elkcub" data-source="post: 1726846" data-attributes="member: 14473">His list was probably intended to rank order the binoculars from best to worst in terms of their inherent lateral CA.  It may have succeeded in ranking the apparent CA to his eyes, but not the actual optical differences between the binoculars.  As earlier posts have suggested there was no control for magnification or FOV.  For a given field angle, apparent CA tends to increase with magnification.  For a given magnification, apparent CA tends to increase with the square or cube (can't remember which) of field angle.  Hand held, it's almost an impossible observation task to judge the extent of CA at a fixed field angle for two instruments (of equal power) with unequal FOV.  Inevitably, the judgment will be influenced by edge differences, which favor the narrower field.  Of course, personal bias (i.e., desires concerning the outcome) also influence the assessment, which is why, in a real experiment, care would be taken to disguise the instruments and use trained observers.  Bla, bla, bla ... :brains:Ed</blockquote>