It was still dark of the moon, so I set up a night shot, plugging the camera and AC adapter into my big battery. The total exposure time was more than six hours (you can see the detailed information below). Then, with the camera chugging away, we went to dinner.
The stars in the Phoenix area are bright in the night sky, but there is also a fair amount of ambient light pollution—which takes down the contrast between the dark night sky and the circling stars. I adjusted for this by exposing at a lower ISO (200) than I would normally use for this kind of shot (ISO 400 is my typical setting).
There was not as much foreground activity as the lights in the composite image seem to suggest. Looking at the individual frames, two cars went by in the course of the six hours—one belonging to a neighbor, the other our return from a very pleasant dinner.
If you look at this image larger, you can make out a barrel cactus in the foreground (Barbara lovers her cacti—and I’d do anything to get this plural form of cactus into a blog story!)
Here are a couple of other long composite exposures of circling stars: Death Valley Star Trails and Valley of Fire Star Trails. If you are interested in this kind of photography, please consider joining me in November at Star Circle Academy below Mount Whitney in Lone Pine, California.
Exif data: 10.5mm digital fisheye, 95 stacked 4 minutes exposures for a total composite exposure time of 380 minutes (6 hours and 20 minutes); each exposure at f/2.8 and ISO 200, tripod mounted.