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ALFOSC CCD3 known problems and their suggested solution

General recommendations

In case you get a problem with the ALFOSC observing system, this is the recommended order of remedies to try before calling the technical support staff:

  1. Run the offending command or script again.
    If that doesn't work then

  2. Run the command 'restart-ccd3-alfosc' (on tessa, any terminal window). This will restart the ccd3comm program and the database daemon. Look at the "Status Delay" in the CCD3 Status Display. It will count up to about 7s, and the system is ready again. Consider waiting until the on-going exposure is finished before doing this, as any exposure will be lost. If this dosen't work then

  3. Shut down the observing system and start it again.
    Doing this up to three times can get things going again. If that doesn't work then

  4. Shut down the observing system, log out of Lisa, log in again and start the observing system.
As per MAY 2015, the different daemons associated with the ALFOSC observing system are restarted automatically. There is no need to manually restart them anymore if they crash.

Specific solutions to known problems

  • If the "Status delay" number on the ccd3 status display is red and is counting up then shut down the observing system and start it again.

  • if you see error messages in the Talker like this:

    [ERROR:] Cannot create WCS information for this image (system is 2). xbin is 0. Looks like the CCD status database is not updated.

    then shut down the observing system and start it again.

  • If you see error messages in the Talker like this:

    Command timed out looking for CCD3 program (alfosc-ccd3) to talk to (bus=

    Then re-run the command or script that caused the error. If it doesn't fix the problem shut down the observing system and start it again.

  • If you repeatedly and after each restart of the "fitswriter" program gets this error:

    [ERROR]: alfosc-ccd3-fitswriter disconnected from This program must be restarted

    Then the value of one of the FITS keywords is likely causing problems for this program. The solution (for the technical staff!) is to find the offending keyword and comment it out of the fitswriter configuration file "ccd3-alfosc:/etc/ccd3/fitswriter.conf".

  • If you get errors like this:

    [ERROR]: Failed to connect to database: Error: User 'ccd_user' has exceeded the 'max_user_connections' resource (current value: 50)

    restart the fitswriter program as described here here and restart the ccd3db program as described here here

  • If you do not get the prompt back when using the exposure commands ('expose', 'dark', 'mexpose' or 'mdark') and the images are not present in the normal image directory (/data/alfosc), then there is a problem with the "remsave-client". Contact the support staff.
    Note that the images made are, in fact, being exposed and stored locally on the 'ccd3-alfosc' computer. They can be manually copied from 'obs@ccd3-alfosc/images' to 'obs@tessa:/data/alfosc'.

  • If you see images that has horizontal streaks from stellar images trailing towards the right (like this) then shut down the observing system, power the CCD controller off, wait 5 seconds and power it on again. After this you can start the observing system again and continue.
    The CCD controller is the blue box mounted on the right side of the ALFOSC CCD camera. See this photo

  • If you notice that the readouot speed is not what you expect (FPIX=129 (or other) instead of FPIX=200), do (in this order) 'resetxy', 'readspeed what-you-want', 'resetxy'. Only after these commands should you set/change the binning if needed.

  • When windowing the ccd, set the X and Y size (with 'xsize' or 'ysize') before setting the beginning of the window (with 'xbeg' or 'ybeg').
    If you do the reverse and start an exposure, the software will freeze when starting to read out the image. If this occurs the image is lost and you have to restart the observing system.

  • When changing readout speed to 800 kpix/sec using the command 'readspeed 800' always remember to give the command 'ampl A' (or 'ampl B' if you want to use that amplifier) afterwards.
    If you do not, the bias level will be wrong.

  • Changing readout speed changes the overscan value from 10kADU to e.g. 12kADU, 16kADU, 23kADU or 4.294903E9ADU, depending of the combination. You can normally recover to the 10kADU level by giving command e.g. "resetxy" or "xbin 1".

Back to top Last modified: 18-Oct-2016