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Message: <blockquote data-quote="elkcub" data-source="post: 1310507" data-attributes="member: 14473">Kevin,Developing a technical argument based on one's inability to see something may say more about viewing conditions, optical quality, or the observer's vision, than the phenomenon being addressed.  I must say that S. Ingraham's article has always been somewhat opaque to me, partly because I can't see any difference (there we go again) between the first and second set of star test images.  Having no figure captions to go on, I'm not sure but that we interpret what he didn't say quite differently.  The figures below were taken from Henry Paul's 1963 Binoculars and All-Purpose Telescopes.  Panel (f), with a split star image, comes from a "poorly made roof prism" (courtesy Zeiss).  The roof line shown in the second image seems to be what AP is always able to see, and you can see only some of the time.  I have a hard time seeing it at all, even on cheap roofs.  So, I'm not convinced that the star-test images and roof line visibility are directly related.     Incidentally, although it's off-topic, the first experiment on adaptation to inverted images was reported by George Stratton in 1896 — before any work on disoriented chickens was done.  (attached)  <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" />Ed</blockquote>

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