found this on geekologie today, thought it was pretty spiffy. From the photographer:
The time-lapse sequence was taken with the simplest equipment that I brought to the star party. I put the Canon EOS-5D (AA screen modified to record hydrogen alpha at 656 nm) with an EF 15mm f/2.8 lens on a weighted tripod. Exposures were 20 seconds at f/2.8 ISO 1600 followed by 40 second interval. Exposures were controlled by an interval timer shutter release (Canon TC80N3). Power was provided by a Hutech EOS203 12v power adapter run off a 12v deep cycle battery. Large jpg files shot in custom white balance were batch processed in Photoshop (levels, curves, contrast, Noise Ninja noise reduction, resize) and assembled in Quicktime Pro. Editing/assembly was with Sony Vegas Movie Studio 9.