While trying to photograph meteors in the Perseids shower recently I ended up taking a lot of longish exposure photographs of the same patch of sky. I was hoping to catch a meteor or several shooting though the frame. Reviewing the photos when I got home I found I caught no meteors, indeed I saw none either, but I did have a set of images I could make a star trail image from.
The usual way to make star trail images is to load the separate images into layers in Photoshop or Gimp and them blend them together. I’ve since found a nice piece of software that automates this process, StarStaX. The following two images were generated with this software. I only had a small number of images usable for the stacking, and there were quite large gaps in time between image, so the results are not as great as they could be. This is not the fault of the software.