With our values from Table 3.2, the RC case with m2 = —4 and Ra = +0.225 gives 0.921 for the factor in the bracket. With m2 ^ ro, it becomes unity, giving the same result as the classical telescope because the forms are identical in the afocal case. In the focal case, the CFP is slightly nearer to the secondary than is the prime focus. The same situation applies to the position of the exit pupil ExP if the entrance pupil is at the primary. Applying (2.94) and Fig. 2.13, we can derive, making use of the paraxial relations (2.90), (2.55) and (2.72), the relation
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