: Richard Harrington's Blog
: Combining Multiple Photoshop Layers with Statistics
People often enjoy star trail photography, and that works great, but rather than having to do everything in camera, where you take a multiple hour long exposure and you might get it right, I'm going to show you how simple this is to do by just shooting a time lapse sequence. What you can do is easily capture several images over time and then blend them together. Here's how.
Combining layers with statistics from Learning Photoshop Automation by Richard Harrington