User's Guide to the Lick 36" Refracting Telescope

Slit (shutter)
Lens Cover
Position Indicators
Tangent Arm
Access Ports
Control Desk
Observing Hits
Trouble Shooting

Mt. Hamilton Homepage

Pointing Limits

The 36" has several sets of pointing limits. These limits are governed by the mount design, cables, railings, slit and windscreen heights, available ladders, and floor travel.

The mount type is an German Equatorial mount. It has a pier that runs up through the middle of the dome. This creates a dead spot where the telescope cannot cross the meridian. From hour angle 40 minutes East to 40 minutes West you cannot point the telescope 30 degrees North to 44 degrees North without great care. When one gets close to these limits one needs to look up to the railing on the pier to see if the tangent arm (or any other part of the telescope) is going to have a collision with the railing.

The telescope has a few power cables that cause pointing restrictions. One should not operate the telescope north of 16 degrees declination and east/west 3 hours when under the pier (Figure 1 shows the telescope near the -3 hours +16 degrees declination limit). If one needs to be at +18 degrees declination and 4 hours over then the telescope needs to be "reversed". See reversal for the procedure. Figure 2 shows a diagram of the pointing limits and restrictions for the telescope.

The minimum declination is governed by the slit height. The lowest one can get a clear view out of the slit (limited by the wind screen) is -35 degrees declination. There is no upper limit but the dome needs to be rotated often when near the zenith. The lowest declination for which the telescope is easily accessible when the floor is at its maximum height is -23 degrees (when on the meridian, see Figure 3). To access the telescope instrument at lower declinations one must use a ladder. Ladders range from a 3 step step-stool up to the original 8 foot tall wood ladder (see Figure 4). The 8 foot ladder will allow a taller observer to get to -40 declination.

Figure 2: Pointing limits. Blue region denotes area where telescope can be on east or west side of the pier ("observing under the pier"). Yellow region depicts the "dead zone" where one may observe with extreme caution to be sure that the telescope does not collide with the railing or other structures of the pier.

Figure 1: The telescope "under the pier" near the -3 Hr and +16 Dec limit.

Figure 3: Floor limits. Line denotes lowest declination that can be reached from the floor at the top of its travel as a function of hour angle. Reaching lower declinations requires a ladder.

Figure 4: The ladders available in the dome.