Trouble Shooting



Fault Reports
If none of the following helps, please look at the archive of resolved fault reports and if you cannot find what you need there, fill in a new fault report.

Other sources of help
Before calling for technical support at night, trying running the commands FAULTS on the TCS console (i.e., MAIA) to get a log of known outstanding problems.

Telescope problems
SERVO FAULT or BUILDING DRIVE FAULT lamps at startup
Running DIAGNOSE
Primary mirror support pressure
Focus control
Tertiary mirror
Cannot find CALIBRATE POINTING star

DBS problems
DBS control computer
Autoguider not working
Stars look very dim on autoguider

CCD problems
Excessive noise in image or obvious bias structure (HWINIT)
Aborting exposures part way through. See Known problems page.

Software problems
Xgterm graphics screen colours not set up



  • SERVO FAULT or BUILDING DRIVE FAULT lamps at startup
    If the SERVO FAULT lamp is lit, press SERVO FAULT/RESET to attempt to clear it. If the BUILDING DRIVE FAULT lamp is lit, press TELESCOPE SYSTEMS OFF, BUILDING DRIVE RESET and then TELESCOPE SYSTEMS ON. Even if it is not possible to clear the fault(s), continue startup anyway, and later run the DIAGNOSE program to gain further information. In most cases this will inform the observer of the nature of the fault and the subsequent course of action.

  • Running DIAGNOSE
    The telescope systems diagnostic program called DIAGNOSE is run automatically at startup. It can be run at any time by entering the command
    TEL$ DIAGNOSE
    This program tests the various status bits and information signalled to the computer by the TELESCOPE SYSTEMS and reports any malfunction or abnormality it finds. If faults exist, it issues appropriate error messages and often suggests action to be taken by the observer with message in `brightened' text. Finally it concludes with a summary of the telescope state displayed in inverse video. It will be one of the following:
    Test sequence failed - TELESCOPE SYSTEM UNUSABLE
    Telescope systems functioning and ready for observing
    Telescope systems abnormal but observing may be possible

  • Primary mirror support pressure
    The primary mirror support pressure sensor sometimes gives inaccurate readings. If the TCS gives a warning message about the primary mirror support pressure, it is probably OK. Best to mention it to technical support anyway.

  • Focus control
    At times the focus control buttons at the console fail to move the focusser. This problem appears to be located within the Auxiliary Systems Cubicle, but the exact cause has not yet been identified. Until it can be fixed, control of focus is best restored by turning Telescope Systems off, waiting a few seconds, and turning them on again. It is not necessary to shutdown the control software, so you will not lose aperture calibrations etc.

  • Tertiary mirror
    The tertiary mirror may on occasion drive to the wrong position when a particular Nasmyth focus is selected. More commonly, it will correctly stow itself if the primary mirror covers are closed during the night, but refuse to return to the correct location when they are re-opened. Should this happen, issue a new
    TEL$ CONFIGURE FOCAL_STATION NASMYTH_A
    command or close and re-open the mirror covers using the SWITCH command instead of the normal console button.
    TEL$ SWITCH MIRROR_COVER CLOSED
    TEL$ SWITCH MIRROR_COVER OPEN
    It is possible to move the tertiary manually from the Auxillary Systems Cubicle downstairs, but this must be regarded as an absolute last resort as it is believed to make the problem worse.

  • Cannot find CALIBRATE POINTING star
    If the star is not visible in the guider, check all the usual things like RA/dec, Epoch, filters, exposure time, MaxIm DL display grey-scale settings etc, and then the following.
    i) Try exposures of different durations and look at the sky value, to ensure light is getting through the system.
    ii) Is the star simply hidden behind the decker?
    iii) At the TCS type
    TEL$ CALIBRATE POINTING/SHOW
    to get the current pointing constants. Write these down in case changing them just makes things worse. You can always reset them to these initial values later with
    TEL$ CALIBRATE POINTING Xc Yc
    where Xc and Yc are the values you just copied down.
    Compare the values you have to those on the white board in the control room. Set the values given for Nasmyth_A on the white board using the above command and try to acquire the star again.
    iv) Choose another star in a different part of the sky
    v) If none of the above helps, it looks like pointing is a long way off for some reason. Select yourself a very bright star and you'll just have to hunt around until you find it.

  • DBS control computers
    Any problems with the DBS control computer should be easily fixed by closing down the control programme with the FILE -> EXIT menu and restarting it. Should the PC itself need to be rebooted, it is located in the DBS electronics rack on the Nasmyth platform.

  • Autoguider not working
    If the autoguider does not appear to be moving the telescope....
    Have you run ENLIST TXA6 on the TCS?
    Do you have only one copy of MaxImDL running on the PC?
    If the answer to both of the above is `yes', close down MaxImDL, close down any other applications running on the PC and restart the auto-guider software as per instructions in the auto-guider manual. If this does not help, re-read the auto-guider manual in detail.

  • Stars look very dim on autoguider
    If you can only find very bright objects in the autoguider, or nothing at all....
    Check the TV filter in the DBS hardware control is set to CLEAR. If it is, select another filter setting and return it to CLEAR again to make sure the display is updating correctly.

  • Excessive noise in image or obvious bias structure (HWINIT)
    The CCD controller sometimes creates considerable noise in the form of coarse horizontal striping, which cannot be corrected by bias frames. (It looks a little like a badly tuned TV signal). It is normally cleared by resetting the ASTROMED controllers with the "Initialise CCD Hardware" option in the CICADA pull-down menu. The bias structure is usually not sufficient to make running new bias frames in the middle of the night worthwhile at the expense of observing.

  • Aborting exposures part way through
    See Known problems page.

  • Xgterm graphics screen colours not set up
    If all the colours in the gterm window are the same so that your IRAF plots are invisible, you need to set up your Xdefaults. In your home directory, edit the file .Xdefaults. First check the end of .Xdefaults. Some accounts have been set up with default colours that gterm does not like. If they exist, comment out the following lines with an `!'.


    Now issue the command
    xrdb .Xdefaults
    to update the new settings and restart IRAF in a new xgterm.

    If the above does not help or you still do not like the colours, add lines such as


    and then re-run xrdb as above.


    Last modified: August 10, 2005