corresponding, in the Cassegrain case, to an ellipse with (bs1)TC,0 = —0.578 with our standard values of Table 3.2 with m2 = —4, Ra = 0.225. With these values, the secondary has the form (bs2)TC,0 = +1.667, a fairly steep oblate spheroid, but not nearly as steep as the form required for the SP telescope of Case 6 in Table 3.2. The equivalent Gregory case with m2 = +4 and Ra = — 0.225 gives (bs1)TC,0 = —1.422 and (bs2)TC,0 = +0.600.
The field coma of such a TC,0 telescope is given from Table 3.5 as tc,o = — I fO (dl£ + y)
Substitution for £ and di f
from (2.72) gives
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