From: "Ted" <tjswift@ucdavis.edu>

Date: January 26, 2008 12:18:47 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Astro IIDC, occultation, and time

I'm interested in doing occultation timing, and just learned that

Astro IIDC can time-stamp each frame. This makes me wonder if it might

work for occultation timing, and make the whole setup much simpler and

cheaper (a digital video camera and a laptop, instead of a analog

video camera, GPS clock, time-stamp inserter, video to Firewire

converter, and laptop). My question is: Has anyone figured out how to

synchronize the Mac's clock to NIST or GMT closer than the ~half

second or so we can do over the Net? I'm confident an occultation's

duration could be measured to an accuracy related to the frame rate,

but the occultation's absolute start and stop time would be uncertain

by that ~half second or so.

  I guess another question is: What's the most light-sensitive

Firewire or USB camera that works with Astro IIDC? I just looked up

the DMK 21AF04, and it says its sensitivity is 0.5 lx at 1/30s, with

gain at 20 dB (100x?). Several other cameras look like they're in the

same range. A lot of occultation trackers are using the Supercircuits

pc-164c analog camera, which reads down to 0.0003 lux (though I don't

know how good the signal-to-noise is there). The 164C can make out

stars down to about magnitude 9-11 with a moderate sized scope.

  One hybrid possibility would be to use a low-light analog camera

like the PC-164C, a video-to-firewire converter, and Astro IIDC. Has

anyone tried this kind of thing? Thanks.

-Ted