Time-Lapse Techniques — Creating Star Trails
The stars wheel above the Cretaceous-age sediments of Dinosaur Provincial Park.
One of the most powerful techniques in the nightscape photographer’s arsenal is to stack lots of short-exposure images together to create the equivalent of one long exposure showing the motion of the stars. A creative tool to do this in Photoshop is the “Advanced Stacking Actions” from Steven Christenson who maintains a blog and eStore called Star Circle Academy.
I used one of his Actions to create the feature image above. Unlike more run-of-the-mill stacking procedures, Christenson’s nifty Actions can create star trails that look like comets or streaks fading off into the sky at their tail end. It’s a clever bit of Photoshop work achieved by stacking each successive image at slightly lower opacity.
You can use his Actions to create a single composite still image, as above, or to create a set of “intermediate” frames that can be turned into a time-lapse movie with stars turning across the sky and drawing trails behind them. My movie shows several variations. Click the Expand button on the movie to have it fill the screen and reveal the sub-titles.
In Clip #1 I stacked the original set of 360 images without any trailing, using the original frames that came from the camera, albeit with each frame processed to enhance contrast and colour.
In Clip #2 I stacked the images using the “Comet Trails” Action, one that produces very short comet-like streaks.
In Clip #3 I used the “Long Streak” Action to produce longer star trails, but the process also creates unusual cloud streaks as well. Rather neat.
In Clip #4 I used the more conventional “Lighten Mode” to create trails that accumulate over the entire sequence and never fade out. The result on this night was pretty wild and excessive, with the twilight and moonlight adding other-worldly colours.
I certainly recommend the Star Circle Academy Photoshop Actions. While there is a basic Test Set available for free, the full Advanced set is well worth the $30.
– Alan, June 1, 2013 / © 2013 Alan Dyer