Coude Auxiliary Telescope User's Guide

Table of Contents

Optical Arrangement
Bore Sighting
FAT-CAT (Wide field acquisition camera)
Image Rotator (Hamilton Manual)

Observing Hints (Hamilton Manual)
Old Cat Manual
Hamilton Spectrograph Instrument Manual

Data Archive
Mt. Hamilton Homepage

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.