Hi Tom,
If you are timing lunar impact flashes I guess a timing accuracy of only 0.1s is required to confirm a simultaneous event but researchers may prefer to 0.01s for light curve analysis.
Analogue video at 50 fields per second gives exposures of 0.02s per field, which is the fastest rate currently used by most occultation observers. All these GPS-linked VTIs have an accuracy of 1 – 100 microseconds.
For more information on VTIs and video camera timing delays (internal delays and integration effects) have a look at the work of Gerhard Dangl (AT) here.
Cheers,
Alex.