Star trail photos are a type of  astrophotography that focuses on the paths starlight creates in the night sky over a period of time. With a long exposure time, a camera trained on the night sky will catch the arcing trails of light from stars as the earth rotates, leaving circles of light on the image.
With the time-lapse technique, you can take periodic shots of the same scene using longer exposures that keep a camera sensor exposed to light for 30 minutes — or even shorter four-minute-long exposures. Then you can merge this series of images in Adobe Photoshop to capture hours’ worth of star movement.