You probably know that Polaris--the North Star--remains stationary in the night sky, and all of the heavens rotate around it. If you could lie under a cloudless sky at night for several hours, you would see the stars spin around the sky like they were tracks on an old vinyl record. Perhaps it has occurred to you that this would also make a great photograph. In the past, I've told you about how to take other sorts of night photos, so this week let's see what it takes to shoot star trails.
The Beauty of Stars
I have to admit that I find star trail photography to be intoxicatingly beautiful. Not only do these photos capture the essence of motion in a still frame, but they also hint at the enormity of the galaxy we live in, and the mathematical precision of the universe.
The trick to capturing star trails, obviously, is to shoot a sufficiently long exposure to capture the motion stars make in the sky as the Earth rotates on its axis. (Yes, to be clear, star trails are formed by the relative motion of the Earth, not the stars. The stars are relatively fixed in space. But I digress.)
The Basic Tools
You can shoot star trails with any digital camera that allows you some measure of manual control over the shutter and aperture, so a digital SLR or an advanced point and shoot is best. You'll also need to set the camera on a tripod, of course--no hand-held shots for this particular project. I highly recommend having a way to remotely trigger the shutter. If you have to touch the camera to take a picture, you risk moving the camera, and as you'll see, moving it even a little can be a problem, depending upon the method you choose to capture the stars. See if you can get a remote trigger cord or a wireless remote control for your camera. Finally, since you'll be doing this outdoors, in the dark, bring a flashlight.
Once you've got all your basic supplies, pack it in the car. You probably won't be able to get very good results in your backyard, unless you live in a very remote area. You'll want to get far away from the light pollution caused by civilization. You'll get the best results well outside any city or town about 600 years ago. If your time machine is broken, then you'll have to settle for just being far away from city lights here in 2011.
Choosing a Shooting Method
There are generally two ways to shoot star trails: with a single long exposure, or by combining many shorter exposures and "stacking" the photos together on the PC afterwards.
Both methods have their pros and cons. Stacking is sort of like making a panorama or a high dynamic range photo, so it requires some additional software. And if you bump the camera even once in the middle of an evening of star trail shots, the whole series is ruined. Also, stacking works best on cloudless nights, because a single cloud wandering through your shot can ruin the final photo. But in my opinion, those difficulties are more than worth it, because the alternative method--a single long exposure--will generally suffer from too much digital noise and light bleed (unexpected light pollution "fogging" the scene) to be useful.
If you're just looking to get your feet wet, though, taking a single long exposure is an easy way to get started. Set up your camera, point it at the sky, and set the ISO as low as it will go to minimize the inevitable digital noise. Set a middling f-number (around f/8) and then expose the scene for about 15 minutes; you might get something like my photo on the left.
If you like what you see, and the noise isn't terrible, try a second exposure at around 30 minutes. Now you might see something more like my photo on the right.
Stacking a series of shorter exposures has a lot more potential for jaw-dropping photos. If you want to try this approach, increase the ISO to a much higher value--say, 400 or even 800--and open your camera's aperture to its largest f-number, such as f/4. Set your shutter speed to 30 seconds.
Now you're ready to take your raw footage. You'll want to take more or less continuous photos for the next 30-90 minutes (or however long you can muster the patience to babysit your camera in the dark, in the middle of nowhere). If you have a remote trigger for your camera, you can set the camera to its continuous shooting mode and "lock" the remote so it takes photos one right after the other. If you don't have a locking remote, then you will have to hold the button down for an hour, and that's no fun. Another option: check your camera's user guide to see if it has an "intervalometer" feature, which lets you program it to shoot a sequence of photos automatically.
When you have a hundred (or so) photos and you're ready to stack them, you'll need some stacking software. I have used StarStaX and Startrail--both are good programs, both are easy to use with handy tutorials, and both are free. Using either of these programs, you can make some impressive photos, like this one.
Hot Pic of the Week
Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique.
Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 800 by 600 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.
This week's Hot Pic: "Lazy Sea Lion" by Robert Berger, New Jersey
Robert writes: "I took this picture on San Cristobal Island in the Galapagos Islands, off the coast of Ecuador. I used a Panasonic DMC-FZ18. The animals in the Galapagos are unafraid of humans, so they do as they please."
This week's runner-up: "Leiria Castle" by Tom Thompson, Hamilton, Ontario
Tom writes: "While on vacation, I took this picture from my hotel room, which overlooked a castle sitting above the town of Leiria, Portugal. I shot it with a Canon Rebel XTi and balanced the camera on the hand rail to minimize shake."