DESIGN METHOD OF AN ASTRONOMICAL TELESCOPE WITH REDUCED SENSITIVITY TO MISALIGNMENT

Approximate formulas are derived for the axial coma resulting from til t and decenter of a surface and for the spherical aberration resulting from a change in its axial position. These expressions include terms that represent aberrations induced by the subsystem preceding the surf ace in addition to other terms that are intrinsic contributions from t he misaligned surface itself. This separation of the terms gives a sim ple method of designing a system that is insensitive to a misalignment at a given surface. The method is illustrated by applying it to a two -mirror astronomical telescope with corrector. Two examples are given- one for tilt and the other for despace. In both examples an appreciabl e reduction in the sensitivity is obtained. The limitations of these s olutions and the problem of simultaneous correction for two types of m isalignment are examined.