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Message: <blockquote data-quote="elkcub" data-source="post: 1348278" data-attributes="member: 14473">Ron/Ron,I'm still quite befuddled.  The correctness and value of the procedure doesn't add up for me, yet.  Again, why doesn't this rather straight forward procedure show up in optics books?  |:S| I came across an interesting and possibly relevant passage in H.R. Suiter's book Star-Testing Astronomical Telescopes, pg. 52, concerning "Stacking of MTFs."  Here he points out "As long as optical difficulties are independent of one another, the total MTF of the system is just the individual MTFs multiplied together..." according to a recipe involving n successive MTF degradation factors.At first blush that would seem to foreclose the use of a booster because the MTFs can not be multiplied in a coherently coupled system (see above).  The aberrations would interact and not be independent.  However, he then proceeds to explain that astronomical telescopes are designed with objectives and eyepieces separately optimized, because one doesn't know what will be hung on the end of the objective.  "Some optical devices, particularly those without interchangeable eyepieces, have optics designed as a unit.  Aberrations inherent in the objectives are canceled by oppositely directed aberrations in the eyepiece or other tailpiece optics.  .... When trying to use the degradation equation for such optics, the evaluator must be careful to circumscribe the whole system—not just part of it."  Hope spings eternal.  The implication might be that since the binocular and booster are separately optimized that the degradation equation for the two in tandem might be applied as he appears to do with astro telescopes.  The dilemma for me is that it's not clear why separate system optimization makes for aberration independence.  Hypothetical questions:  If telescope A had known aberrations and telescope B were perfect, would it make a difference which one was used as the booster for the other?  If they both were imperfect, but in different ways, would the order reveal a difference?  Cheers,Ed</blockquote>

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