STF-8300M camera. I am doing some drift scan studies and I need to know the exact start (or end) of an exposure (down to a few msecs). I noticed in the FITS header the line TIME-OBS='10:33:46.479', does this mean the time is known precisely to the microprocessor to 1 msec? If so, how would I then set the microprocessor time to 1 msec with a GPS? Given the delays in the PC/USB/microprocessor I can see all sorts of delay issues. Another method would be if there is some signal (maybe the Guide connector signals?) which could indicate precisely when the integration begins (or stops), I could then monitor this with an external analyzer and superimpose its signal with GPS timings to precisely determine the start (or stop) time of the camera.