Common Problems

It will be noted that many of the following problems have a common cause - dirt on the encoder strips. Each telescope axis is fitted with an encoder strip that, when dirty, prevents the reading heads from correctly determining telescope position, thus causing problems during both initialisation and tracking. The problem should not affect observations significantly, although it is generally more pronounced following a period of rain or high humidity. Generally, the quick fix is to re-initialise the telescope, although the only real solution is for telescope staff to clean the encoder strips (this is done periodically throughout the year).

Note that, in the following, 'TCC' refers to the Telescope Control Cabinet, which is the electronics cabinet on the top floor of the tower.

• Brakes do not release. Most likely, a brake power fuse has blown. This can be confirmed by checking the LEDs labelled ``BRAKE POWER'' on the back of the TCC. If any have blown, see appendix E and ask for assistance.
• Motors do not move. It is probable that a motor fuse has blown. Check the fuses in the TCC (see appendix E). If any have blown, ask for assistance.
• Telescope cable pipe switch light is on. This refers to the big cable hanging under the teescope counter-weight. Simply move the cable to fix this. If you need to open the cable box, ask for assistance.
• Telescope repeatedly fails to initialise. When the telescope fails to initialise it is due to dirt on one, or both, of the encoder strips. Usually, simply re-initialising is enough. However, if the encoders are particularly dirty it may be necessary to use the service program (see appendix B) to move the telescope a substantial distance in both axes, and then re-initialise.
• Coords look OK but software is reporting a long time to target. This is probably because the telescope has initialised with incorrect azimuth coordinates (+ or - 360 degrees). Park the telescope and check the azimuth axis on the turret diagram. The value in red reports the last known azimuth position, used during initialisation. If this looks wrong, you must change it in the config (see appendix C) before re-starting the software.
• Telescope misses target. Sometimes the telescope will appear to initialise, but will then be unable to find a target. This means that the telescope has initialised with incorrect coordinates and needs to be re-initialised. (This is why it is important to check telescope coordinates straight after initialisation.)
• Telescope moves away from target during observations. Again, this is most likely due to dirty encoders in either the azimuth or elevation axes. Re-initialisation is required. If it is 12am exactly, however, the problem has a different cause, and re-setting the target is all that is required (parking is not necessary).
• Red Schupman crosshair on finder display does not point exactly to target. This is because the telescope is not perfectly calibrated (see section 4.2). There is no quick and easy solution for this.
• Telescope has hit an end-stop. When the telescope is against an end-stop, it must be moved in the opposite direction with the handpaddle. Use the service program to do this (see appendix B), and then restart the turret program.
• Telescope won't initialise and prints message. ``DAC has no power'' Check the green LED on the DAC chasis (located in the corridor between the control room and the optics room). If it does not have power then check the fuse (see appendix E) and power input.
• Motor current exceeds 500 while telescope is tracking. This means that one of the telescope motor fuses has blown and should be replaced (see appendix E). Ask telescope staff for help with this.
• Handpaddle doesn't work. The batteries may be depleted. Fresh batteries should be available in the control room (see 4.6). If an actual fault has developed, ask staff for a replacement handpaddle.
• Power to azimuth axis 'wobbles'. This could be because you are tracking an object too close to the zenith (overhead point). Objects cannot be tracked in the 'zenith blind spot' because the azimuth axis is forced to move too rapidly.
• No active regions. Sometimes there simply are no active regions on the sun. Otherwise, the turret computer has failed to collect the active regions text file from the NOAA website (which it does every night at 4am via ftp). To update the file manually, use the button on the Red Hat toolbar. If this is successful then the active regions can be loaded into the turret using the button on the top toolbar.
• Software crash. If this happens, it is very important to reboot the machine (royac27) before restarting the program. royac27 can be found in the corridor between the control room and observations lab.
• Turret computer malfunction. If the turret computer (royac27) develops a fault, then the backup machine (royac26) needs to be installed in its place. This should simply be a case of swapping all the cables from one machine to the other and logging in as obs like usual, but please contact staff before attempting the switch.