User's Guide to the Lick 36" Refracting Telescope


Introduction
Dome
General
Floor
Slit (shutter)
Windscreen
Rotation
Lighting
Telescope
General
Balance
Lens Cover
Motion
Position Indicators
Finderscope
Tangent Arm
Reversal
Access Ports
Control Desk
Console
Contents
Limits
Pointing
Weather
Safety
Observing Hits
Checklist
Trouble Shooting

Mt. Hamilton Homepage

Troubleshooting

RA won't unclamp
Floor won't move
Tracking doesn't work
Floor starts slowly sinking
Telescope is tracking at the wrong speed


RA axis won't unclamp

If the RA axis won't unclamp it is possible one of the three clamps is not fully releasing. First try clamping then unclamping the telescope again, as this can vibrate the sticky clamp and loosen its motion. If that fails after a couple of tries, try slightly moving the telescope back and forth in the RA direction, which may free up the sticky clamp and try unclamping again. If this still fails, contact a telescope technician or support astronomer.


Floor won't move

There are three different cases of floor movement failure:

  1. Won't move at all.
  2. Will go up but not down.
  3. Will go down but not up.
The first case is the most common. If the floor won't move at all one should first check that there is power. The orange power indicator light on the desk console should be lit. If it is not lit, turn on the console power. Odds are good that someone tripped one of the pressure safety switches for the floor, which turns off the main power to the dome (which includes the floor motion).

If the power is on and the floor still won't move, try using the other floor control switches (either on the desk console or the telescope paddle). It is possible there is a wiring problem making one set of controls inoperative.

If the floor still won't move, contact a telescope technician or support astronomer, as the problem is probably with the compressor or hydraulic ram presses.

The second case, where the floor will go up but not down can be caused by two separate problems. It could be one of the buttons is failing to actuate. In this case simply try the down button on the desk console or telescope paddle. If the floor still won't go down, it means that the lower limit switch is stuck in the triggered state and the mechanism thinks the floor is already all the way down. You will have to go to the basement and find the limit switch (it is just below the floor level underneath the wrought iron stairs up to the catwalk) and exercise it to get it unstuck. If this fails the switch is likely broken and will need serving by a staff member.

The third case, when the floor will go down but not up can have three common causes. First, as above, the floor up button may have failed so try the up button on the desk console or telescope paddle. If the floor still won't go up, it may be that its limit switch is stuck in the up position. The upper limit switch for the floor is located on the telescope pier to the upper right of the desk at the catwalk level (it is difficult to access the limit switch when the floor is down because it is high on the pier). If the limit switch is not the problem, then the problem is with the compressor or hydraulic ram presses which raise the floor and a staff member will have to investigate the problem.


Tracking doesn't work

If the telescope isn't tracking check the following:

  1. Make sure the RA clamp is on.
  2. Make sure the tracking power supply is on.
  3. Make sure the tracking switch is on.
  4. Check that the motor is actually running (it makes a characteristic hum when operating).
If the motor is not running but everything else it on, it is likely that the tracking motor breaker has tripped. To reset do the following:
  1. Turn off the tracking motor.
  2. Go to the room just below the top of the pier.
  3. To the left, near the breaker box on the far wall, is a box mounted on the wall. This is the tracking motor reset box. Push the "Reset" button on the box and power should be restored. For images see access ports.
  4. After resetting, go back to the desk console and turn the tracking motor power back on. With luck tracking will be working. If not, contact a telescope technician or support astronomer.


Floor starts slowly sinking

On occasion the floor will start slowly sinking when not commanded to move. This usually occurs when there are too many people on the floor or when too many people are clustered in one spot. The floor sinking is not dangerous to people on the floor, but since the floor is not under active control this can be a hazard to people trying to enter or exit the floor as well as the fact that the safety pressure switches will not stop the floor from moving when they are actuated, which can be a serious safety problem.

The easiest way to stop the sinking is to command an upward move of the floor to restore pressure in the hydraulic ram presses.


Telescope is tracking at the wrong speed

If the telescope is tracking at the wrong speed check the following:

  1. Make sure the RA axis is clamped.
  2. Make sure tracking motor is on and set to track (you should be able to hear the motor running).
  3. Make sure the tracking speed is set at sidereal rate (or lunar rate if looking at the Moon).
  4. Make sure sidereal tracking speed is set at 15 arcsec/sec (or very close to this). If the sidereal speed is not close to this, it was probably adjusted for a non-sidereal target, such as a comet. Go ahead and set it back to 15 arcsec/sec if necessary.