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New types of prime focus field correctors for Ritchey–Chrétien telescopes are described, which have substantially better imaging than those at present in use. Examples are an improved corrector for the |f/2. 7| focus of the Cerro Tololo 4-m telescope, and a wider field | (2^_. 0) | corrector for the Anglo–Australian telescope.
C. G. Wynne (Sun,) studied this question.