The field coma effect is, in practice, relatively modest. With the normalized data of Table 3.2, the basic Schiefspiegler term of Eq. (3.356) gives +48.871$, corresponding to the aplanatic telescope, while Eq. (3.358) for the classical telescope gives +45$. This is a measure of the seriousness of decentering coma, the basic decentering effect being, in the configuration of Table 3.2, over twelve times as serious as the field coma of a classical telescope associated with the same beam angle upr x.
For the general case of a 2-mirror telescope with secondary defined by bs2 and corrected for spherical aberration, we have for the lateral decentering tangential coma
(Comat)s = A - BS1 - BS2 = (Comat) s,ci - BS2 (3.360)
From Eq. (3.358) and the second term of (3.355), we have
This reduces to the simple general form
or the angular form
Was this article helpful?