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You Are Here:  Home  >  FAQ  >  Photography Techniques  >  Photographing Star Trails

Photographing Star Trails

Table of Contents

Chapter Word Count: 2835
1 Introduction  (131)
2 Time-Lapse of Milky Way over Idaho  (472)
3 Photographing Star Trails  (691)
       3.1 Composition  (565)
       3.2 Exposure Times  (295)
       3.3 Powering the Camera  (468)
       3.4 Fogging Lenses  (196)
4 More to See (17)

This page has 13 images dated from
Sep 19, 2003 to Aug 18, 2009
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1 Introduction

Photographing the night sky is extremely rewarding because you often get views of things that your own eyes either can't see, or you don't think to look for them. When seeing photos of stars, star trails, or other night images, people are often surprised by the unreal—or surreal—colors. They often think these photos are either fake or manipulated. While that could be the case, what most people don't understand about light is that the human eye doesn't discern between the chemical compounds that make up light. Humans view a very narrow spectrum. Cameras, on the other hand, can pick up light wavelengths that is composed of chemical compounds like helium, hydrogen, and so on. These chemicals change the "color" of light that that we can't easily see, but cameras can.

Because our everyday world doesn't have a lot of things that are heavily weighted towards these things, most everyday pictures that we take appear much like we see them in real life. But it so happens that stars in the sky are different—they are made up of gasses that are comprised of these chemical compounds that emit colors that we can't see, but cameras can. So, the "hues" you may see in photos of stars may appear vivid, but that does not mean it's been artificially altered.

Star Trails
Exposure Time: 15 minutes
(Death Valley, California, USA)
california, death valley, horizontal, long exposure, national parks, nite, star trails, stars, west coast, western usa, photograph
Star Field
Exposure Time: 25 seconds
(Death Valley, California, USA)

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 15 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. For comparison, a close-up photo of the moon can only be about 6 seconds before the Earth's movement blurs it. Part of your experimentation will be to gauge the timing for how much "trail" you want.

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Click for time-lapse movie
(King's Canyon National Park, California, USA)
california, galaxy, horizontal, kings canyon, lodge, long exposure, milky way, nite, stars, west coast, western usa, photograph
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Click for time-lapse movie
(King's Canyon National Park, California, USA)
california, galaxy, horizontal, kings canyon, long exposure, milky way, nite, stars, trees, west coast, western usa, photograph

The above photos were taken at King's Canyon National Park in California, with a setting of 30 seconds at f2.8, using an ISO of 3200. The camera I used is a Canon EOS 1DsMark3, however any camera that can do 30 seconds at f2.8 should get pretty good results, provided the sky is cooperative. A fun thing to do with these "still" photos of star feilds is to use a cable release with an interval timer to take a series of consecutive pictures and string them all together in a movie. In this case, I created a video consisting of about 210 photos, each taken exactly the same way. Since each exposure is 30 seconds long, the entire sequence took 120 minutes, or about two hours. Click on the photo to see the movie. Once the individual frames are captured, you can use a variety of editing tools to string them together into a video format, such as Apple's iMovie program, which is included with the computer, or any number of applications. Search for "movie editing software" on the net. All of them can produce movies from still frames like this. I happened to use a program called "FotoMagico" on my Mac.

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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)
africa, kilimanjaro, mountains, nite, star trails, stars, tanzania, vertical, photograph
A time-lapse movie can capture the sky moving as a series of photos, but capturing this movement in a single picture is called a "star trails" photo. There are two ways to do it—one is by taking a single "long exposure" photo, and the other is to take a series of photos (like above) and then sandwich them together into one photo. Here, the consecutive sequence of stars will mesh together to look like trails. The first method is far easier, but not everyone's camera can do long exposures well. There are two problems: the longer the exposure, the more noise there is in the resulting photo. Higher end cameras don't suffer from this as much, but those with lower-end cameras may be quite unsatisfied with the results. The other problem is that some cameras can't do exposures longer than 30 seconds, making the multi-exposure method the only option. Of cours,e the other side of the coin is that multiple-exposures requires dealing with a lot of files and getting familiar with photo-editing software in order to make the final image. So, there are upsides and downsides to each method. This article only addresses the long-exposure technique, not the multi-exposure sandwiching technique.

The process for taking long exposures in a single frame is technically simple. You only need a camera that can has the "bulb" exposure setting, and a cable release. Generally, you set the camera on the widest aperture setting your lens can do, press the cable release, and go get coffee, or have dinner, or go to sleep. Many star trails pictures are hours long. Once you try this, you'll be instantly excited by the results. However, if you're like most people, you will also find you've made a few mistakes, or that the exposure didn't quite come out right, or that the focus is just a little soft, or that your foreground objects (not stars) aren't what you hoped they'd be. This is why this article goes on.

To avoid many of the common mistakes with star trails photos, the main things to keep in mind are:

  1. Sensing the ambient light
  2. Composing the scene and setting camera controls properly
  3. Focusing on the right spot
  4. Experimenting a lot

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Redhorse Mountain Ranch
(Red Horse Mountain Ranch, Harrison, Idaho, USA)
america, fisheye, fisheye lens, horizontal, idaho, long exposure, milky, north america, red horse mountain ranch, scenics, united states, way, photograph
As noted above, the first problem most people find is that their exposures don't come out quite right. They're either too dark or too light. If it's too dark, you need to open up your aperture more to let in more light. If it's too light, it's probably because there's ambient light in the sky you didn't anticipate. This light may come from nearby cities, the diminishing sunset an hour or more afterwards, or the moon (even if it hasn't yet risen in the sky). 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 10 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 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 close to it on either side) 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.

Using a flashlight, wave it around inside a tent for about 30 seconds. (20-minute exposure.)
(Death Valley, California, USA)
california, death valley, long exposure, national parks, nite, star trails, stars, tents, trails, vertical, west coast, western usa, photograph
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.

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.

Two Hour Exposure out a hotel room window
(Alto Adige, Italy)
alto adige, dolomites, europe, giau, gusela mountain, italy, long exposure, nite, pass, passo giau, star trails, stars, vertical, photograph
Most people use the Polaris, the northern hemisphere pole start as a point of reference for composition decisions. As the Earth rotates, stars will appear to spin around it, as shown in the photo of Gusela Mountain, in the Italian Dolomites. (Those who live in the southern part of the planet don't technically have a southern pole star, but they do have "The Southern Cross." The southern celestial pole can be located by extending the line from Crux Australis (the Southern Cross) approximately 5 times the distance between the two stars to reach the position of the pole. Alternatively, bisect the 'Pointers' and draw a line from that point to intersect the line from the Southern Cross. They intersect at the pole.)

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.

One reason why long exposures are hard: there are many things that can ruin your picture... like a late-night car driving where it shouldn't be.
(Logarska Dolina, Slovenia)
dolina, europe, horizontal, logarska, logarska dolina, long exposure, nite, slovenia, star trails, stars, photograph
Because of the different sources of light and the great effects such subtle changes can have on a very long exposure, you can't really "calculate exposure times" here. The camera's light meter is irrelevant, especially for exposures that are going to be well into the minutes, if not hours. This requires setting the shooting mode to "manual" or "bulb" and using a cable release. Some advanced cable releases have timers built into them, whereas manual versions require you to push the cable yourself. If you think that's not so bad, keep in mind that you're going to have to be around (and awake) in several hours when you want to release that button. Every camera manufacturer has different cable releases to choose from, but after having done this for a while, I can speak confidently that having one with a timer is well-worth the money.

At this juncture, you must now experiment and rely on trial and error to learn the ropes. Just compose what you might think would work, release the shutter, and go get coffee (or go to sleep).

It's tempting to want to use a higher ISO setting to brighten photos due to the lower light conditions, but the side-effect of higher ISO is higher noise. I use ISO 100 to keep the "digital noise" down, which is more pronounced in darker areas of an image than lighter ones. Your mileage may vary, as different camera manufacturers deal with noise differently. Even though some cameras may perform better than others, all cameras will produce much better images at lower ISOs than higher ones.

3 Hour Exposure Facing East (North Star is upper-left, southern point is below horizon on bottom-right.)
africa, desert, dunes, horizontal, morocco, sahara, sand, startrails, photograph
There are two ways to power cameras: batteries, and direct plug-in to a wall socket. First, the batteries:

Almost any film-based SLR will expose long enough because battery consumption is low. But digital cameras have a tougher time because digital sensors eat power. Most consumer-brand cameras won't do much more than about an hour or two on a single charge, but that gets better as technology improves over time. You'll have to experiment. Higher-end ("prosumer") cameras can do much better, but on those cameras, there's another factor: noise reduction. Long exposures often cause the camera to take a second "dark frame" (internal) exposure for the same amount of time as the first exposure, which it then uses as a mask to cancel out the noise. You don't do this yourself—the camera does it automatically— but it means that a 1-hour exposure requires 2-hours of battery life to process the photo to the end. So, if you're going entirely from battery power, you may be limited.

To get more images in less time—and to make the most of battery power if you're not using a power adaptor—opt for simpler night pictures of shorter star trails, or just star fields. As stationary objects, it's still a pretty amazing site.

For those using pro-level Canon equipment, I can vouch for my 1DsMark3 and 5DMark2, each of which will easily do a 2+ hour exposure, plus the added 2nd "dark frame", on a full battery charge. I can't speak to other camera models or brands.

If your camera comes with an direct AC power adaptor that allows you to plug the camera in directly to the wall, you don't have a problem with power. However, it means that your location is limited to one that has proximity to an outlet. To optimize this flexibility, get one of those 100-foot long extension cables at a home supply store or even drug stores. Not all cameras have such an adaptor—especially the lower-end consumer brands—so if you're in the market for a new camera, be sure to look for this.

When staying in hotels, I often choose rooms that face towards the darkest part of the sky and that have the least amount of ambient light (usually the decorative hotel lights). This way, I plug into the wall, and place the camera (on tripod) either on the balcony, or shoot through the window. When camping, I use an AC power adaptor plugged into the car or a nearby power supply. (A house, cabin, etc.) Obviously, this may not always be possible. In this case, true night-photo nuts go out and buy generators or battery packs that can keep a good exposure going for quite some time.

During a full moon, exposures can only last about 8 minutes before over-exposing.
horizontal, latin america, long exposure, massif, nite, patagonia, star trails, stars, torres, torres del paine, trails, photograph
A common problem with night photography is dew fogging the glass because ambient air is warmer than the lens itself. What causes dew isn't the temperature, it's the amount of humidity in the air (though cold fronts tend to have drier air). Metal lenses will always be colder than the ambient temperature, but even lenses with plastic barrels can suffer from the problem simply because of the glass components inside the lens. The solution is keep the lens warmer than the air. How you do that is the challenge. The most fool-proof way is to get a bulky battery pack and wire it up to your lens. Places that sell astronomy equipment make these for larger telescopes, but they are too large for normal camera equipment—it'd be like shooting a mouse with an elephant gun. The solution "works" and won't damage anything, but it's an overkill.

Light trails on the ground were from the flashlights pointing down used by people walking by.
(Yosemite, California, USA)
california, light streaks, motion blur, nature, nite, plants, sky, star trails, stars, trees, upview, vertical, west coast, western usa, yosemite, photograph
20-minute exposure of star trails, with trees lit by faint ambient light from the campfire
(Yosemite, California, USA)
california, horizontal, nature, nite, plants, sky, star trails, stars, trees, upview, west coast, western usa, yosemite, photograph

4 More to See

For a complete list of all star trails shots on this site, go here.

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