
6.4. Three-Mirror Telescopes 149
The first telescope of the PB type built is the CCD/transit instrument
described by McGraw et al. (1982), and located at the Steward Observatory of
the University of Arizona. This telescope has a
1.8"m//2.2
primary with
k ^ 0.32, and near-diffraction-limited images over a 1° field of view. Because
of the baffles required to prevent light reflected directly fi-om the primary or
tertiary fi-om reaching the detector, the vignetting by the central obscuration is
approximately 22%. For further details, the reader should consult the article by
McGxdm etal (1982).
There are several examples of PB designs in the literature ...