Photographing Star Trails PART I, by Dan Heller

1st Introduction

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star "field," a static snapshot of the stars as points of light. Star Field(Death Valley, California, USA. Visit aouthor Dan Heller

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star "trails," where the stars' movements streak across the sky. Star Field(Death Valley, California, USA) Visit author Dan Heller

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When photographing stars, you can either get a star "field," a static snapshot of the stars as points of light, or star "trails," where the stars' movements streak across the sky. How long you expose the image determines which you get. The first rule of thumb to remember is that the Earth rotates such that the light from a star begins to "move" after about 30-40 seconds. (It's apparent movement is largely dependent on your lens—the longer the focal length, the more apparent the movement; the wider angle lenses won't show much movement till later because of the star point is so small.) Part of your experimentation will be to gauge the timing for how much "trail" you want.

My very first truly successful star trails picture: a 3.5 hour shot on a night with no moon, 16,000 feet above Mt. Kilimanjaro(Kilimanjaro, Tanzania) Visit author Dan Heller

Photographing star trails is technically simple; the main things to keep in mind are:

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- Timing the light
- Compositing the scene
- Watching battery power
- Experimenting a lot

Most people who get started with shooting star trails want to capture the longest trails they can by keeping the shutter open longer. The inherent problem with this is underestimating the ambient light in the sky, even though you don't necessarily see it. This light may come from nearby cities, or even the diminishing sunset an hour or more afterwards. What your eye sees is nothing compared to a long exposure of a camera, where this residual light can be so overwhelming, you don't see any stars at all. A 20 minute exposure an hour after sunset can look like a day shot, and if the moon is anything more than crescent, you'll be limited to just a few minutes at best. (By comparison, a full moon will make a night shot look like a day shot in about 8-10 minutes at f2.8 at ISO 100.)

Picking a faraway place on a night with a new moon (or where the moon hasn't yet risen, or after it's set) is best for getting the darkest skies, which make the light from the stars is more pronounced. This may not be as easy as you think. The photograph of the lit tents shown here was shot in Death Valley (over 300 miles away from Las Vegas), which still had an illuminating effect on the horizon. To illuminate the tent, I spent about 30 seconds waving a flashlight around from inside the tent. This process is hard to get right without overexposing the tent's fabric. Again, the benefits of experimentation. This light also helped bring out detail on the ground.

1.1 Composition

Using a flashlight, wave it around inside a tent for about 30 seconds. (20-minute exposure.) (Death Valley, California, USA) Visit author Dan Heller
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While photos of nothing but star fields and trails are fascinating and will impress your friends and neighbors, they can get pretty old pretty fast if that's the only thing in your photo. These pictures are much better with foreground subjects. Think daytime photography here: a lake, an interesting tree, rock formation, or even your house. As you experiment with various shots, the first thing that'll pop out at you as you see the actual photos, is the direction of the star trails themselves. This is never apparent when shooting the picture because you don't actually see the stars move at all. Hence, the direction of where the stars move will become an increasingly important element in choosing your compositions.

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On a perfectly dark nite under a totally new moon, you won't have much to see other than stars. With no other light at all—even the ambient light—you can't see other objects at all in the foreground, which makes for limited composition options. Here, it's common to get a silhouette of a tree or a mountain. Although it's also fun to use a flashlight to illuminate foreground subjects like a cactus. (I've even used the brake lights and turn signals from my car to create colorful red and yellow bursting effects on foreground objects.) Starting an exposure while a crescent moon is just about to set can illuminate the foreground enough to have them lit adequately, while permitting the exposure to continue (and get longer trails) as it gets darker.

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Two Hour Exposure out a hotel room window (Alto Adige, Italy) Visit aouthor Dan Heller

Most people use the Polaris, the northern hemisphere pole start as a point of reference for composition decisions. (Those who live in the southern part of the planet can use the southern pole star.) As the Earth rotates, stars will appear to spin around it, as shown in the photo of Gusela Mountain, in the Italian Dolomites.

In choosing foreground subjects, you'll need to make sure you get them in focus along with the distant stars, which often requires smaller apertures. This works against you because the smaller aperture means less light. Alas, your composition has trade-offs: composing a scene that can uses a wide aperture, but still has interesting foreground subjects. Generally, I compose scenes that have the closest subject to the lens be at least 10 feet in front of me, if not further. I also use a wide angle lens, so that I can get everything in focus at or f3.5 up to f5.6. I try to avoid apertures greater than f8, which can yield a reasonable picture if exposed for several hours or more. Again, I don't want to raise my ISO setting, because the digital noise becomes intolerable. However, doing so is a good way to experiment, and get a prototype of what your composition will look like for a longer exposure at a lower ISO.