The CAT has five reflections (six when used with the
image rotator, not shown here).
The mirrors are referred to as CAT mirrors 1-5, in order of
occurence along the lightpath. They are listed below, along with their
associated covers. The steps for
opening and
closing the telescope are
described in the body of this manual.
CAT mirror #1, also called the siderostat, is the only
moving mirror in the optical train. It is a large, equatorially mounted,
rectangular flat, to the south of the 3-meter dome. When not in use the
siderostat is protected by a mirror cover and housed in a sheet-metal
shed, both of which are rolled clear for observing. When pointed to the
target, the siderostat tracks the object and directs its light through
an opening in the side of the dome, called the upper shutter.
The
upper shutter is kept closed when the CAT is not in use,
to prevent rain or fog from entering the dome. When open, light from the
siderostat passes to CAT mirror #2.
CAT mirror #2 is a fixed, circular flat, just inside the
south wall of the 3-meter dome, that turns the siderostat beam, sending it
vertically downward to the CAT mirror #3.
CAT mirror #3 is the telescope's fixed, upward-facing,
0.6-m, f36, primary mirror. When not in use it is protected by a pneumatically
operated cover.
CAT mirror #4 is the telescope's fixed, downward-facing
secondary mirror.
The
portal cover lies between CAT mirrors 4 and 5, on the
ceiling of the coude slit room. It is manually opened for CAT operation.
CAT mirror #5 is a small, rectangular flat that turns the
nearly-focused CAT beam toward the coude spectrometer's entrance slit. It
is manually swung into position and uncovered for CAT operation.