I've always enjoyed playing around with long exposures, and for a while I've been working on my star trail photos. Taking a single very long exposure is impractical, because the sensors of digital cameras overheat and add bright purple clouds of color to the image. So, the solution is to take many shorter photos, and "stack" them together into one photo.
In order to take that many photos, I needed a way to control the camera. Some cameras have built-in features to do this, but in my case, I used gphoto2, which I previously used to take some time lapse videos of the Portage Lake Lift Bridge.
This photo is a stack of 40 images, each of which was a 30-second long exposure at f/3.5 and ISO 400. Things did not work out perfectly: my camera went crazy at one point (gphoto isn't perfect), and after 20 minutes my battery died (I failed to fully charge it before!). I've learned a lot, so I'm planning to head out and try again next weekend!