Today was the Hack Day at dotastronomy. An incredible number of pitches started the day. I pitched using webcam images (behind a fisheye lens) from the Liverpool telescope on the Canary Islands to measure the sidereal day, the aberration of starlight, and maybe even things like precession and nutation of the equinoxes.
I spent much of the day discussing and commenting on other hacks: I helped a tiny bit with Angus and Foreman-Mackey's hack to sonify Kepler data, I listened to Jonathan Fay (Microsoft) as he complained about the (undocumented, confusing) Astrometry.net API, and I discussed testing environments for science with Arfon Smith (github) and Foreman-Mackey and others.
Very late in the evening, I decided to get serious on the webcam stuff. There is an image every minute from the camera and yet I found that I was able to measure sidereal time differences to better than a second, in any pair of images. Therefore, I think I have abundant precision and signal-to-noise to make this hack work. I went to bed having satisfied myself that I can determine the sidereal period, which is equivalent to figuring out from one day's rotation how many days there are in the year. Although I measured the sidereal day to nearly one part in 100,000, my result is equivalent to a within-a-single-day estimate for the length of the year of 366.6 days. If I use more than one image pair, or span more than one day in time, I will do far, far better on this!