Creating Star Trails

Star trails are a fairly easy 'showy' photograph to create. You need three things: a camera with manual settings, a tripod, a place with visible stars. This technique, however, is also good for other composites. The basic premise is to take a lot of photos in rapid succession, stack them all, and then erase all of the parts that are the same on each layer. This leaves the unique elements from each image and allows a photographer to capture long exposures without some of the long-exposure issues such as calculating film ISO and exposure times.

Step 1: Find a location that you think will yield interesting results. Even for your first image, interesting results are worth shooting for. There's a chance you'll get a great shot and the good results will likely spur you on to try again and improve from your previous efforts.

Step 2: Set up your trip pod and frame the shot through your camera. If you are going to do this on a new moon and don't have good lighting for your subject (e.g., if you're in a remote location without bright enough lights to yield good visibility through your viewfinder), set it up during the day, note your direction and tripod settings, and then return at night and re-apply the settings.

Step 3: Take a test shot. For star with no other light, I find that 30 seconds slightly stopped down (say f4) is pretty good. But take a test shot and adjust your settings until a single image looks good. Then set up your camera to take a LOT of photos. Most high-end DSLRs have a built-in intervalometer. An intervalometer takes a series of photos at a set interval. My K-7 can take up to 99 images with a minimum of one second between each image. That means that every 51 minutes and 15 seconds, my K-7 takes 99 images. So, if you want nice, long trails that require about 300 images to take, it will take about three hours and three intervalometer resets.

If your camera does not have a built-in intervalometer, you will want to buy one. Most purchased intervalometers run in the $15 to $35 range. These will typically take up to 399 consecutive images. So, set up your intervalometer and get ready.

Note that on my first image attempt I put five seconds between images to help keep the sensor cool. This was a HUGE mistake. The trails all had noticeable gaps between them that I couldn't get rid of. The image was taken over six hours with 400 images or something. 400 images times about 45 stars per image means I would have had to manually fill in 18,000 gaps. Pass.

Step 4: Take a series of images.

Step 5: If you have an EXTENDED version of one of the recent Adobe Photoshop versions (I have CS 4, so at lease CS 4 and later), you can automatically make star trails in Photoshop. Note that every time I've tried this in Photoshop without using a custom extension, I've had AWFUL results. So I use the Star Trails Stacker by Floris script for Photoshop. There are a number of free programs JUST for star trails photos, too. So you can do this without investing $700 in Photoshop.

Step 6: Blend the images. God help you if you elect to do this by hand. Assuming you use software, mess around with the settings and see what results you find the most visually appealing.

There you go -- a star trails image.In essence, it's just a lot of shots stacked and blended. Unless you have a film camera, then things get interesting.


This image was taken with 260 five- or six-second captures. This was more an experiment to capture airplanes landing at SFO. The stars were an added bonus.


This was an intentional star trail but with an accidental gap in the middle. The image itself isn't very good, though.