Hey Guys, Just spotted this thread. I'll try to clear up a few issues now, but if I havent, please remind me!
Ron - You are dead right. Don't get hung up on timing. Observing the event is the most important thing. And report it even if you had a 'miss'.
I'm going to do my sums in PAL (25fps) please convert if necessary.
PAL takes 25 frames every second. That means that each frame is 40ms in duration. The half frame accuracy means that if you 'know' that the event happened on a certain frame (the extinction of most stars is as good as instantaneous), then the reported time is the median time +/- 20 milliseconds. Interlaced cameras like the GSTAR-EX actually take two FIELDS per frame, so it is possible to get a timing of +/- 10 milliseconds or 0.01.
Back to reality - if you are not using specialist timing equipment, you are unlikely to realise these numbers. there are inbuilt latencies in any computer system and AV is designed to be self healing it will insert duplicate frames or loose the odd one as it sees fit if the system so that it can maintain a steady stream.
Beeper Sync will do a fantastic job of setting your pc clock, and let you know its level of accuracy. Unfortunately the beep coming out of your computer is when your commuter decides based on processor priorities, and not when the actual time occurred - it may not be far out, but who knows. Beeper boxes are designed to overcome these issues but unfortunately Pauline is inbetween batches.
But Bojan, if you capture using GSTAR capture (free from the myastroshop website) it has built in millisecond timing overlay from the computer clock and I recommend giving it a go in conjunction with beeper sync.
To be honest, the old method of using a tape recorder and just shouting gone and back when the event happens with a short wave radio time signal in the background is plenty good enough…
I have a youtube channel with a few of these things: http://www.youtube.com/user/astrojunk