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Message: <blockquote data-quote="elkcub" data-source="post: 3172539" data-attributes="member: 14473">All,After reading Suiter's "Star Testing Astronomical Telescopes," 1994, several years ago, it became clear to me that his emphasis was entirely on telescope objectives.  Briefly reviewing his logic:  <ul> <li data-xf-list-type="ul">In the last paragraph on Pg. 37 he says: "The filters covered in this book concentrate on the center of the stack, from the atmosphere down to the image inspected by the eyepiece." [see below for the "stack" of filters] </li> <li data-xf-list-type="ul">On Pg. 38 (top) he says: "Eyepieces are neglected here..."  </li> <li data-xf-list-type="ul">Throughout the book he relies on photographs, implying that the camera is an adequate simplification of the eye.  </li> <li data-xf-list-type="ul">His regard for the eye in the astronomical observation task is foreclosed in the next to last paragraph on Pg. 37: "The only things that can be done ... for the awkward distribution of low-light sensors on the retina is not to look directly at dim objects." [hic !] </li> <li data-xf-list-type="ul">With regard to MTF graphs he states (Pg. 53): "... This book concentrates on the theoretical description of ideal cases."  In other words, the graphs are generated from theoretical equations, not empirical data.</li> </ul>So, when he gets to the topic of "Filtering of Spherical Aberration" (Pg. 176, Fig. 10.5), which Henry included above, we are looking at his generalized theoretical curves pertaining to telescope objective aerial images, devoid of influences by eyepiece or eye.    For these reasons I'm befuddled by how far these graphs can be generalized to low-power birding binoculars, much less how perceptions at the end of the filter stack can be predicted or better understood.  Suiter simply doesn't mention terrestrial binoculars, ... the ones we look through that have all those nasty effects he avoided.  Don't get me wrong, I'm not against star testing.  But I do appreciate Warren J. Smith's admonitions in "Modern Optical Engineering," (1990), pg. 501. (second attachment)  Ed</blockquote>

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