The Schmidt camera is particularly advantageous in certain astronomical and spectrographic studies. This paper gives an exact derivation for the equation of the correcting surface, together with some approximations rather more precise than those previously available. Performance of actual instruments made according to the old and new equations will differ significantly if the surfaces are figured with exceptional care.
FRANK ALLEN LUCY, "Exact and Approximate Computation of Schmidt Cameras," J. Opt. Soc. Am. 30, 251-254 (1940)