Diameter of the Schmidt corrector lens.

The Schmidt-Cassegrain 'R' kit above is based on a design by H.G.J. Rutten who modified the original design of Slevogt, in 1942. The kit includes the primary mirror with a molded curve and matching tooling, the secondary mirror with a molded curve and the matching tooling, a corrector blank with related tooling. All of the tools are made out of plate glass.

For a review of the design, please read the following:

H.G.J. Rutten and M.A.M. van Venrooij, "Optical Performance of Astrocameras", Telescope Making 18,pp. 12 - 19.

H.G.J. Rutten and M.A.M. van Venrooij, "Telescope Optics, Evaluation and Design' (Willmann-Bell, Inc., Richmond, Virginia), Chap. 9 - 11, pp. 79 - 111.