Star trails are pretty cool, there’s no doubt about it. A well-executed star trail image gives the viewer a sense of infinity, of the universe on its eternal march through time. But sometimes you don’t necessarily want star trails in your photos. They’re cool, but they’re not what you see with your own eyes when you look up at the sky. Instead, you want to capture the beauty of the night sky as it really is. But here’s the problem: it’s dark, the stars move, and they move quickly. How can you capture them without a long exposure?
The Milky Way by Flickr user Kiwi Tom
Any exposure time of more than, say, 1/60th of a second (that varies of course depending on the length of your lens, but as a general rule …) requires a tripod. You’re not going to be shooting with super long exposures, but the exposures will still be long enough that you won’t be able to shoot handheld. So a good, sturdy tripod is going to be an essential piece of equipment.
Along with a tripod you will also need to have a remote release. This is important especially for exposures in excess of 30 seconds, when you have to switch to bulb mode. Bulb mode requires you to either press the shutter button once to open the shutter and again to close it, or to keep the button depressed for the length of the exposure. Either way, you can’t do this with your self-timer. So having a good remote release is pretty essential for this sort of photography.
You will also need a camera that lets you take manual control over your settings—that usually means a DSLR or an advanced compact camera. Remember that you can’t really trust your meter after dark, so you don’t want to depend on your camera to guess at an exposure. You’ve actually got a pretty limited range of settings you can use before you start to get star trails, so it’s really essential that you can shoot in manual mode.
Finally, you’ll need a fast lens, but it will also have to be capable of shooting wide. So a basic 50mm prime is not going to be wide enough—you need something more in the 14 to 24mm range because the wider the lens, the longer you can leave the shutter open before you’ll start to see star trails. So look for a wide lens but also one that has a large maximum aperture—the closer you can get to f/2.8, the better. This is really important for capturing the night sky without star trails, because you need to allow as much light as possible to enter the camera in a relatively short period of time.
Milky Way and radar dome atop Mount Laguna by Flickr user slworking2
Some things to consider first
If you live in the city, you already know what one of the big problems with stargazing is in your local area: you can’t do it. There are no stars in the city, or if there are they are just a scattered few of the brightest ones in the sky. Starscapes and city lights don’t play well together. That’s what they call “light pollution,” which simply means that all those artificial lights that come from street lamps, skyscrapers and automobiles leak into the night sky and interfere with the visibility of what’s up there. Smog is a contributing factor, too—all that murky brown stuff that sits on the horizon during the day doesn’t go anywhere at night, instead it blocks even more of the natural light that otherwise should be coming from the stars. So if you live in the city, you’ll need to plan a trip out of town—way out of town.
It’s not really enough to just get in your car and start driving, though, unless you happen to have special knowledge of a place where there is very little light pollution and a clear view of the night sky. If you’re not sure, there are some light pollution maps online that you can consult when making your choice (the Blue Marble map comes to mind. Just zoom in on your location and pick a spot nearby that’s black, then do some research into those areas to determine where the most scenic areas might be. If it’s a familiar place that might be an easy call, otherwise try searching Flickr to see where other photographers chose to shoot similar images.
Natural settings work best for star photography of any kind, not just because you’ll get a lot less light pollution in a natural place but also because natural beauty helps to compliment that fantastic beauty that’s already present in the night sky. So this isn’t the sort of photography that you can really just blunder into, you need to spend some time planning.
Racetrack Stars by Flickr user David Kingham
The next thing to think about is the phase of the moon. The moon can also be thought of as a source of light pollution—the brighter it is, the more impact it will have on the visibility of the stars. So it follows that if your goal is to capture amazing star photos, you can’t really do that during the full moon—or even when the moon is approaching full. Instead, aim for the night of the new moon, or at most one week before or one week after. Generally speaking, though, the closer you can come to the night of the new moon the better luck you’re going to have capturing those beautiful stars.
Don’t forget that you need clear skies, too. In a pinch you can shoot on a partly cloudy day but for the best images you really do need to be shooting in completely clear conditions. Check the weather before you go—and don’t bother if there’s even a slight chance of precipitation, because that usually means too many clouds in the sky.
Stars over Yosemite by Flickr user Christopher.Michel
Forget ISO 100, you won’t be able to use that for non-star trail images. Larger ISOs are going to be essential, which means that the better your camera is at handling higher ISOs, the better your images will be. Older digital cameras or less-expensive point and shoot cameras may produce noise at higher ISOs, so although you’ll still be able to capture images of the night sky they’re not going to be as clear as you might like them to be.
Autofocus is out, too. Your autofocus system is great during the day, but at night it’s going to get confused and you’ll probably end up with photos that have the wrong focus point. What you want is a crystal clear shot of the stars themselves, which means you’ll need to turn off autofocus and focus your lens manually to infinity. Now you may have been told that you can line up with the infinity symbol printed on the barrel, but that is not in fact a very accurate way to ensure good focus when you’re shooting something as small as a distant star. That’s because manufacturers no longer bother to individually calibrate each lens they make. Instead, you need to use your eyes to get this right. The best way to do this is to focus on a distant object such as a mountain range during the day, and then mark the barrel with a piece of tape (or a permanent marker, if the thought of marring the pristine beauty of your lens barrel doesn’t bother you) at the middle point of the infinity symbol. Remember that you can set your lens to infinity before you even leave the house, and then you won’t have to think about focus at all once you arrive at your destination. Make sure to do this at your lens’s widest focal length and take a few practice shots to make sure that the focus on that distant object is correct.
Now comes the tricky bit—deciding on an exposure time. Your goal is to avoid star trails, so you need to do a little bit of math. Let’s say that your lens’s widest focal length is 14mm—that’s the focal length you’re going to want to use for these photos. Get your smartphone out (or do some mental math, if you’re good at that) and divide 500 by 14 (you will always use 500 as a baseline). Rounded down to the nearest whole number, the number you’ll arrive at is 35. That’s going to be the maximum shutter speed you can shoot at before you’ll start to see star trails.
For the most part, you’ll want to start at an ISO of around 1000 to 2000 and make adjustments based on your results. Remember that the higher you go the more noise you’ll get, so you may need to do some corrections in post processing to reduce noise. Some cameras automatically reduce the noise that can happen during a long exposure (this differs from high ISO noise) but I recommend turning off this setting because 1) it eats up battery life and 2) it doesn’t always do a better job than what you can do in post processing.
And finally, keep your aperture between f/2.8 and f/4, bearing in mind that the wider the aperture, the more light will reach your sensor and the less time you’ll have to keep the shutter open.
Using those baselines for ISO, shutter speed and aperture, start with a test shot and check your LCD to see what kind of results you got. Make adjustments from there, or better yet, shoot a series of images at varying settings so you can pick the best one once you arrive home and can view your results on a larger screen. Remember that guesswork is the standard way to accomplish great star photos, so don’t worry that you’re not getting perfection in every attempt. It’s going to require some experimentation before you get satisfying results.
Stars over makapuu by Flickr user Tommylege
Bring an extra battery or two—remember that long exposures are battery hogs, and you’ll want to spend a lot of time experimenting once you’ve gone to all the trouble of finding a good location and setting up your equipment. Bring a flashlight (for safety’s sake and also so you can easily check your camera settings) and be prepared to spend some time playing, checking your LCD and reshooting. This is extremely rewarding work once you get the hang of it, so if your first shoot doesn’t yield satisfying results you should definitely keep trying. The night sky is a beautiful place, and once you nail down your settings you’re going to start to be really excited by what you are able to accomplish.
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