Updating DIMM Auto-Acquisition Target Position

Use this procedure if auto-acquisition fails to find and/or lock on to the target star. This may happen is the DIMM webcam was bumped or moved relative to the DIMM pointing. The auto-acquistion algorithm depends on a known position between the DIMM webcam and the DIMM camera itself. The star is found on the webcam, and moved to the [X,Y] position related to its associated ROI.


  • Launch the DIMM software as usual
  • Perform a spiral search using the 'Search' button on the 'Go-to / Move' (a.k.a 'Move Mount') subGUI
    • You may need to perform this multiple times using coarse guess-positions to start. The spiral search field is small before it gives up.
    • The DIMM will automatically center-up and begin to measure on the star, once found
  • Go back to the webcam image, then right-click and save the image somewhere.
    • This doesn't matter, but I have a folder /home/telescope/DIMM/ with dated files, to keep a history.
  • In a local terminal:
    • cd /home/telescope/DIMM/ (or wherever you saved the image)
    • gimp name-of-file.jpg &

  • In the GIMP window, you will see something like this:

  • Now zoom in on the star using the magnifying glass tool, and put the cursor on the eyeballed center of the star:
    • in this example, the center is approximately X=127, Y=141 (bottom left of image window)

  • Login to the dimm computer and launch the configuration file we need to change:
    • ssh -X dimmuser@dimm
    • pass: dimm00
    • cd /local/dimm/current/etc/
    • emacs dimmServer.cfg &
  • Scroll to the 'Auto-Acquisition specifications' section at the bottom
  • Modify the Xtarget and Ytarget values to match those you found in GIMP
    • In this example:
      • Dimm.Acquisition.Xtarget=127
      • Dimm.Acquisition.Ytarget=141
    • Click 'Save'
  • In the other terminal you're running the DIMM Client, type:
    • /home/dimmuser/restart/DimmKillServices restart &
      • This will restart the server/client, and absorb the updated configuration

  • Your auto-acquisition should now work correctly
    • If not, repeat the procedure to re-calculate the X,Y position.
      • Sometimes 1 or 2 pixels may be enough of a nudge, in case the auto-acq lands too high/low/left/right.
      • This will be affected by elevation. A middling EL of 60deg or so should be a good place to measure

-- %USERSIG{SteveAllanson - 2018-01-17}%


Topic revision: r2 - 05 Apr 2019, JohnHill
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