Star trails are a common subject amongst astrophotographers. When they’re not trying to capture the milky way, they’re showing the path that our stars take in the night sky. The process for creating these isn’t dissimilar from shooting timelapse with digital. You take a lot of photos over a period of time and then stack them on top of each other in Photoshop.
But this technique from Nemanja Sekulic shows you a way to do this with just a single image. It’s not going to be a perfect recreation of how the stars move through the sky, but it will let you achieve a similar effect. Nemanja demonstrates how to (mostly) automate the process using Photoshop actions that you create yourself.