Star trail photos can be dramatic, gorgeous depictions of the cosmos. They show how the sky moves as the Earth rotates, and how the stars above us vary so greatly in brightness and color. They also serve brilliantly to fill a frame when it’s not quite dark enough for a great shot of the Milky Way. Plus, they’re like catnip to the social media crowd.
But capturing great star trail images involves a bit more than just opening up your camera’s shutter and then sitting back and sipping beers at the campsite. It takes planning and some diligent, but relatively simple, processing on the back end. I spoke to photographer Harun Mehmedinovic, creator of the Skyglow Project, and British journalist and photographer Jamie Carter, author of A Stargazing Program for Beginners: A Pocket Field Guide, about how to snag epic star trail shots. With their combined insights, you, too, will be able to harness the power of the Earth’s movement for photographic glory!
“The easiest and cleanest way to create a star trail is to concentrate on producing one good long-exposure night-sky image, which, crucially, has something interesting in the foreground.”
As for the old-school single-exposure tactic, both photographers agreed that doesn’t always cut it. As Carter explained, most star trail shots in the old days actually were achieved by opening the camera and keeping it open for hours at a time. “With digital cameras, however, that strategy is much more complicated,” Carter said. “The sensors heat up so much that you get a lot of noise or too much light taken in.”
If you do wish to take a crack at the single-exposure approach, Mehmedinovic suggested setting the camera on a tripod at a dark-sky site (as free of light pollution as possible) during a moonless night. You can set the camera to 100 to 400 ISO, somewhere between f2.8 and f5.6, all depending on the level of light pollution in the area you’re shooting. “Make sure the battery is full, make sure the tripod is fully locked off and set into a place with no vibration — so away from roads, earthquake prone areas, objects that cause vibration, et cetera — and just take a 1-2 hour exposure on ‘bulb’ mode,” he said. “This method requires no post-work on the computer to accomplish star trails, so it’s a good first step, provided conditions are met.”
Although that method can work, by far the best approach — and the one invariably used by the astrophotographers you’re seeing on Instagram these days — is to “stack” multiple exposures into a single image via some specialized software. Here’s how to approach the challenge.
1Find clear skies — and something in the foreground. Obviously, you should have a cloud-free view of the night sky, with as little light pollution as possible (though it is also possible to get good results in cities and suburban areas). “The easiest and cleanest way to create a star trail is to concentrate on producing one good long-exposure night-sky image, which, crucially, has something interesting in the foreground,” Carter said. If you’re in the northern hemisphere, he said, point your camera in the general vicinity of Polaris, near the Big Dipper. This will generate star trails in a circular pattern, as the sky rotates around that spot. If you want elongated curves, point your camera to the south.
Framing the shot is the real challenge. “What can really make a difference in how you compose a star trail is the position of Polaris in the sky,” Carter said. “The further south you are, the lower Polaris is, so it’s much easier to get star trails around a church spire, the top of a building, or a mountain. About 20 degrees either side of the equator is actually ideal, which is one reason why a lot of astrophotograhers travel to create their images.”
Mehmedinovic uses foregrounds to ground viewers and the composition. “An old abandoned barn, say, or a shell of a car, or an interesting rock or natural feature — all of which you can light-paint using a flashlight or headlamp or any other source of light,” he said. (Pro tip: use a Lumecube.) “But make sure the light is consistent. Set [the light] down and leave it alone as the camera shoots. This attention to the foregrounds will let us imagine we are standing there as we look at this image. As you get better, you dig in deeper and try to pick foregrounds that, when juxtaposed with stars, tell a certain story. One should always look for narrative in images; it’s rather easy to execute things from a technical standpoint. Most images lack a narrative.”
2Stick the settings. Before pressing the shutter, you need to get your setup right. Start with a steady tripod (an absolute must) and use the widest-angle lens you have, which will allow you to pull in more of the sky and fold in terrestrial elements, as well. Open the aperture (f-stop) as wide as you can to allow as much light in as possible, then switch the lens to manual focus and fix the focus on infinity. (You can pre-set this while it’s still light by focusing on a distant point, and then fixing the lens with tape so it can’t be adjusted, Carter noted.)
Mehmedinovic recommends f/5.6 at 25 seconds with an ISO of 800. “That should give you decently clean results with most cameras,” he said. “If you own a higher-end Canon 5D Mark III or 5DS, or a Nikon D810/750 type camera — all with full-frame sensors — you can get away with using far higher ISO settings to get more faint stars. But more stars doesn’t equal better results, per se. If you can see thousands of stars, when you stack them they will begin to make the composition too cluttered with lines. Lower ISO is the way to go, stack only the prominent stars and planets and avoid making the frame look too busy.” Shoot in RAW, as well, because this allows you to batch-process your images in image-processors like Photoshop later (and the image-stacking software requires it). In Photoshop you can adjust contrast, brightness, et cetera, across all the images at once.
Next, do your shooting in earnest. Without moving the camera, take between 50 and 300 shots, depending on how long you want the star trails to be. Make sure you leave 15 seconds between shots for the sensor to cool down, but not much longer (otherwise you will get gaps in your star trails). You can reduce vibrations by setting your shutter delay to two seconds, or by using a remote shutter release cable. If you have an intervalometer — some DSLRs have them built in, or it’s an inexpensive accessory — it automates the process so you can leave the camera alone to take photos while you go sleep (or drink).
3Dump everything on your computer. Shooting star trails is essentially the same as time-lapse photography, Carter noted. “Like time-lapses, star trails can be rather monotonous to execute, but the results can be fantastic,” he said.
So once you’re done shooting, bring the image to life on your laptop. In your image editing software, work on cooling the color temperature if there’s light pollution, and suppressing any image noise with the ‘luminance’ tool. Then drag the RAW files into StarStaX (it’s free) by following the program’s instructions. When it’s done processing the images, it will generate a JPG image of all the shots stacked in one glorious frame. Post at will, and revel in the accolades.