User's Guide to the Crossley Telescope

Table of Contents

Ground Level
Dome and Platform
Head Rotation
Dec Tangent Arm
Position Indicators
Mirror Cover
Dome Slit
Access Ports
RA Drive Preload
Operating Limits
New Telescope Drive

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The Telescope: Dec Tangent Arm

The declination motion is limited by a screw which travels in a pillow at the top of the declination tangent arm. This screw is on the polar axle side of the tube about 10' above the polar axle at the top of the tangent arm (Fig. 17). When it reaches a limit in its travel you will get no response from one of the declination buttons. Once this happens, you will have to run the telescope in the opposite direction (i.e., the direction of the only working dec button) for a long enough time to recenter the worm in its block - perhaps a minute - then approximately recenter the object by unlocking the dec clamp and moving the telescope by hand. Once recentered, one usually doesn't run out of dec travel for another couple of nights. Checking the centering at the beginning of the night may prevent interrupting an observation later.

Figure 17