The choice of parameters used in Tables 6.5 and 6.6 is arbitrary and different combinations may be more convenient, depending on the application. The advantage of expressing the system coefficients in terms of m and ft is that certain important conclusions are more easily deduced.

Getting from the system coefficients in Tables 6.5 and 6.6 to the transverse aberrations requires substituting each Bs in turn into Eq. (5.6.8) where, as noted in Section 5.6, s'2/n'2 = kf and yt /y2 ~ 1 /k. Take care to note that Eq. (5.6.8) gives tangential coma; our results are given for sagittal coma. To get the angular aberration as an angle projected on the sky, the transverse aberration is divided by / and any leading minus signs are dropped. Angular aberrations are given in Table 6.7, with quantities in brackets taken from Table 6.5 or 6.6.

Table 6.6

Aberration Coefficients for Two-Mirror Telescopes with S3t = 0°


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