Korsch gives two examples of the application of his formulae above to two three-mirror geometries, shown in Fig. 3.72 (a) and (b). The application of the Korsch formulae to his system (a) is shown in Case 9 of Tables 3.2 and 3.3 for the usual normalization with y 1 = 1 and f/ = -1. The set-up data for the Korsch proposal with f/4.5 are:
m2 = -10 (negative for Cassegrain)
Ra = +0.25 (positive for Cassegrain)
Fig. 3.72. Two 3-mirror anastigmatic, flat-field solutions proposed (1972): (a) single-axis system, (b) 2-axis system by Korsch
Then, from (3.318), m3 = -0.150 , an exact value differing from the value -0.149 given by Korsch. This small rounding error has a significant effect on the remaining values deduced from the formulae, which therefore differ somewhat from those given by Korsch.
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