The script turns on a small red light in the dome using a pdu, then takes a picture with the pier webcam.
I had largely forgotten about this script until the other day when we were sat watching the telescope operate and the red light came on in the dome. My first reaction was to disable the script as it was giving the pdu a hard time.. but then I had the idea of making a time lapse video of a night of telescope operation.
It only took a few minutes to modify the script to save each individual image using the timestamp as a file name, I have previously save the images by Job ID to help with the debugging.. but timestamp makes it much easier for mencoder to read the files in the correct order.
The video clip of the night's operation is below. I think it's quite cool, I'm just a bit gutted that we had cloud for some of the night so we only have about 75% of the jobs we'd expect.
The video was encoded using mencoder in mpeg4. The images are shown at three frames per second. Each frame represents one job.
Thinking about it now, it would be very cool to have a normal time based time lapse.. so you would get an idea of how much time the telescope spends pointing at each object. What the current video doesn't show is that an average Constellation job has an exposure time of a few seconds, where as a Galaxy job may be three minutes per colour channel. Sadly to take a pier cam image we need the red light on, and turning the red light on needs to be synced to the times when the astro camera shutters are closed. I think this would be almost impossible to do. Also not being able to grab frames whilst the astro cameras are imaging would mean you would loose the time scale anyway.