Parabolic mirror cannot create perfect image in a larger distance
from a field of view center without image distortion caused by
so-called coma aberration (this aberration is inherent to all
parabolic mirrors). So it is necessary to use coma-corrector optical
device, which significantly reduces this aberration, when using CCD
camera with large detector.
The lenses used in the TeleVue Paracorr PSB-1100 are significantly
larger compared to the lenses used in e.g. in Paracorr PLA-1100 or
other coma-correctors intended for T-thread mount, so it does not
cause vignetting even on large photographic full-frame
24 × 36 mm CCD detectors. The
adapter for TeleVue Paracorr PSB-1100 is attached to the camera body
by the same way like other adapters for various telescope/lens
standards—using four metric M3 screws. So
replacing of the adapter is very easy and the only tool necessary is
the Phillips screwdriver.
Standard G2/G3 T-thread adapter with Paracorr PLA-1100
(left) and large adapter with Paracorr PSB-1100 (right)
The Paracorr PSB-1100 adapter preserves the required distance
between the thread front side and the CCD detector to achieve optimal
correction of coma aberration of parabolic mirrors. Still the G3
camera body contains enough room for mechanical shutter and a filter
wheel with 5 positions for filters up to 10 mm thick.
G3 camera head with threaded adapter for Paracorr