TAO - Timing refinement

After the end of your first scheduled run using TAO, you may notice that the scheduled observation times do not accurately coincide with the actual times when each exposure is taken, and that the difference between scheduled and actual observation times increases with the number of images already taken. These cumulative timing errors may have several causes which act simultaneously:

The assumed slew time models for the telescope and/or dome do not exactly reproduce the timing of actual motions of the equipment.
Certain equipment parameters in the scheduler configuration file are not accurate enough.
The assumed duration of focus breaks in the scheduler configuration file is significantly different from the actual average duration of a focus break.
There are unmodeled effects (filter change times, shutter times, computer processing times, etc.) which contribute a small cumulative timing error (usually of the order of a few seconds per exposure) with respect to the scheduled times.

After tens or hundreds of exposures are taken, the timing error may grow to tens of minutes. If you take some time to estimate the accumulated timing error per exposure, these errors may be significantly reduced on your next observing runs by adjusting the empirical timing correction parameter in the scheduler configuration file.

Collecting timing data

ACP/PinPoint/MaximDL CCD users (who will use the MU image acquisition script) may extract timing error information from MU log files using the script timing.vbe, which is located in the TAO\schedule directory:

Copy the main MU log file (or download it, in case you use a remote observatory) from its original location to directory TAO\schedule.
Open a DOS window (Command Prompt) and cd to the TAO\schedule directory.
To extract the timing errors from the MU log file (suppose it is called MU_20040824_221932.log), type the command
C:TAO\schedule\>cscript timing.vbe MU_20040824_221932.log
After the script executes, you will see a screen message like this:
Timing data written to MU_20040824_221932_timing.txt
The text file containing the timing data will be stored in directory TAO\schedule, and will consist of two numeric columns (exposure number and timing error in seconds).

TheSky/CCDSoft/Orchestrate users will need to compute timing errors manually as the difference between the actual exposure start times (which are stored in the FITS headers of the various exposures) and the scheduled exposure start times (which are listed in the third column of the scheduler summary file. Note that the image numbers in the file names created by Orchestrate may differ from the numbers on the first column of the scheduler summary file by some constant. The computed timing errors should be saved to a text file consisting of two numeric columns (exposure number and timing error in seconds).