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The method of plate-diagram analysis, as developed and extended by Dr. C. R. Burch, is applied to a general survey of the Schmidt-Cassegrain systems. Explicit formulæ are obtained for the figuring strengths of the Baker astrographic cameras in terms of their two free parameters, for the monocentric Schmidt-Cassegrains and for the flat-fielded aplanats with both mirrors spherical; their distortion is also considered.
E. H. Linfoot (Tue,) studied this question.