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Message: <blockquote data-quote="elkcub" data-source="post: 1106425" data-attributes="member: 14473">Dorian,Regarding this quote I have a few questions you may be able to answer.  As far as I know, the objective, inverting prism, and eyepiece are each potential sources of CA, but I have only a sketchy idea how they combine to produce what we see in the final image.  Do you know how this works?   Are their effects additive?  Multiplicative?  Do such aberration effects reinforce or cancel each other?  What you mentioned above seems to addresses only CA produced by the objective.  It may be incorrect, but the design structure of the typical objective seems to me to favor control of lateral CA, and the design of the typical eyepiece to favor control of axial CA.  My suspicion is, therefore, that low-dispersion (ED) glass might be most effective for control of axial CA when used in the objective, and allow for better control of lateral CA when used in the eyepiece.  I haven't got the foggiest idea how much CA is produced by the prism system, or how relatively important it might be.  If porros show less CA than roofs, however (I'm not sure I believe this), then the inverting system design might be a culprit, in addition to the Abbe number of the prism glass.  If you have insights or references they would be appreciated.ElkPS.  I'm not even sure that asking these questions is the right way to conceptualize the CA issue, particularly if binocular design is a holistic, integrated optimization using trial-and-error or heuristic computer modeling.</blockquote>

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