Correspondence with C.G. Wynne, Imperial College of Science and Technology, acting as a consultant on various aspects of optical design, especially correctors. The correspondents are Redman, S.C.B. Gascoigne, J.D. Pope and H.C. Minnett, A.A.T. Project Manager. The letters include reference to problems with Schott, contractors for the lenses. The papers include data, a spot diagram and a drawing of a test arrangement for prime focus correctors.