Get your cameras ready, astro-nerds: This week brings a regular highlight to space-gazing with the peak of the Perseid meteor shower, and it's expected to be a particularly good one this year.
Watching the meteor shower isn't difficult—go out at night, away from streetlights and clouds, allow 45 minutes for your eyes to adjust, and look up. Getting a picture, though slightly trickier, doesn't have to require hugely professional kit.
"If you spend an hour out there watching the meteors, wrap up warm but you should be able to get plenty of photos," Sam Lindsay, an astrophysicist working at the Royal Astronomical Society, told me. He's not a professional photographer, but has managed to capture the Perseids before with his Canon 600D, and has some tips for other amateurs equipped with a basic DSLR camera and some enthusiasm.
Time & Place
To get the best shot at a good shot, you'll want to go out when it's dark on 11-12 August. The Perseid meteor shower is a stream of debris from Comet Swift-Tuttle, and it's visible every year when the Earth crosses through its path. The shower actually lasts for weeks, but at its peak you can usually see up to 100 meteors an hour. This year, NASA explains that, thanks to Jupiter's gravity pulling the Perseids closer to Earth, we're set to see an increased number of meteors this year, known as an "outburst."
"It's going to be hopefully bigger and brighter, and a bit more spectacular than usual," said Lindsay.
Once you've found your spot, you can set up your camera. What you're aiming to get is an image of the starry sky with that signature meteor streak, probably with something in the foreground—a building, a tree, whatever—to add interest.
One thing you'll most likely need: a tripod, or at least something stable to place your camera on. "Even a meteor, which lasts a blink of an eye, is long enough for a camera to wobble and blur if you're trying to do it handheld," said Lindsay. You also can't tell when a meteor is going to cross the sky—it's a game of chance—so you'll want to leave your camera parked and ready to take repeated shots.
Lindsay also recommends a wide-angle lens if you have one, as the more sky you can capture in a shot, the greater your odds of catching a meteor (or several).
Then, the key thing to getting that meteor streak is exposure time, or shutter speed. You'll need an exposure of a number of seconds, but the exact time depends on the lighting conditions where you are. Lindsay noted that in his previous images, he left the exposure a bit too long, which meant his meteors turned out a little fainter than he would have liked. "A happy medium would be 5-10 seconds," he said. "Long enough that you've got a good chance of catching one, but short enough that they still appear quite bright in the image."
It's best to play around with different exposures and see what works with your environment. If you want to get an image with "star trails," you'll need a much longer exposure—this one from Lindsay is a 20-minute exposure—but be warned, you won't catch a meteor with that.
Once the camera is set up, you can leave it to take photos on a timer, and just lay back and enjoy the view. But there are a few other settings you need to be aware of first.
As you're trying to take photos of something in space you can't yet see, you're going to have to use manual focus. "You can kind of set it to what should be infinity, but it's never quite right," said Lindsay, referring to the setting that keeps all objects at a distance in focus.
The best way to do it is to set your focus, take a picture, zoom in on one distant star to see how it looks, and repeat the process with slightly different focuses until you find the best one. "Kind of like playing optician," said Lindsay.
You might also want to take a few images focused on whatever's in your foreground so that you can later photoshop it onto your meteor-streaked sky.
ISO and aperture
Aside from the length of your exposure, you'll need to set your ISO and aperture. These all affect each other and are something of a balancing act, so getting it right is a process of trial and error. On the one hand, a high ISO means you'll get away with a lower aperture, which also makes your focus better. But go too high on the ISO, and Lindsay warns you're susceptible to noise, which doesn't make for a good image.
This will also depend on your camera, as some handle high ISOs better than others, so play around until you're happy with how the scene looks.
Then you can leave your camera to do the work, and hope that you get some good shots when you come to look at them. A final tip: Take lots.