
202 8. Catadioptric Telescopes and Cameras
Thus the concentric meniscus corrector lens is not a viable option because of
longitudinal chromatic aberration.
There are two methods for reducing the chromatic aberration of
the
meniscus.
One,
proposed by Bouwers, is an achromatic meniscus made of two different
glasses cemented together. In this case the cemented interface cannot be made
concentric with the outer surfaces, and the system is no longer strictly concentric.
If, however, the two glasses have the same index of refraction but different Abbe
numbers, then the cemented lens is still very nearly concentric. This possibility is
discussed b ...