
Chapter 5 Fermat's Principle and Aberrations
At this point the stage is set for a general application of Fermat's Principle to a
surface of revolution and the derivation of its aberrations. The theory of
aberrations, generally called the Seidel theory, is a classical subject and has
been treated in detail by many authors, including Bom and Wolf (1980), and
Welford (1986). Excellent introductions to the theory of aberrations are given by
Longhurst (1967) and Mahajan (1998). The treatment here leads to nothing new,
but the approach is one that leads to results that can be easily applied to optical
systems of specific interest to astronomers