Shooting Auroras with a Digital Camera
This image was shot with a Canon PowerShot G2 with a 35-mm lens set at f/2.0. Despite the camera's slow ISO setting of 50, a 15-second exposure was sufficient to capture this sight because the aurora was so bright.
Sky & Telescope photo by Rick Fienberg.
The age of the digital camera is here. As prices fall, new models appear, and features improve, these cameras are dramatically changing the way amateur astronomers "photograph" the sky. So does that mean a digital camera can be used to capture images of the aurora? Absolutely, though there are some caveats.
Older cameras, particularly the early point-and-shoot models, may not be useful for aurora photography. But before you start looking either for an old manual camera or a new digital wonder, check to see if your current camera can be set to an ISO of at least 100. Higher is better (up to ISO 400 or even 800) but as the image above shows, if the aurora is bright enough, a low ISO will suffice. Take a time exposure of at least 15 seconds. Newer models can expose for up to 60 seconds (which will give you more flexibility), but 15 seconds is okay, particularly if you can set the ISO to a high rating.
Have its focus set to infinity. Most autofocus cameras, when pointed at the sky, automatically drive the focus to infinity; if yours doesn't you'll have to focus it manually.
If your digital camera can do all these things, then you're ready to shoot an aurora the next time one appears.
Most suggestions for auroral photography apply whether your camera is digital or uses film. These include using a fast (at least f/2.8), wide-angle lens, fast film (or a high ISO setting on a digital camera), a sturdy tripod, and a cable release (if your camera can take one). And don't forget to bracket your exposures that is, shoot a variety of exposures that can range from 5 to 60 seconds in length.
Mont Cosmos Observatory in St-Elzéar, Quebec, is silhouetted by the ghostly greenish glow of an aurora on April 20, 2002. Philippe Moussette
recorded this scene with a Nikon Coolpix 995 and 30-second exposure at ISO 400.
Some comments, though, are applicable only to the digital domain. For example, when the camera operates in time-exposure mode, noise in the form of bright, randomly spaced pixels can appear in the image. The longer the exposure, the more apparent the noise. (Of course, if the aurora is bright enough, you won’t see the noise!) Most new digital cameras have noise-reduction settings that automatically come into play during time exposures. But be warned: there's a catch. Once the exposure is finished, the camera generates a "black" image that enables it to eliminate the noise in the original image. That "black" image takes just as long to generate as the length of time of your original exposure. So if you take a 60-second shot of the aurora, you'll have to wait another 60 seconds for the camera to "do its thing" before you can shoot again.
Something else to keep in mind is that digital cameras can get warm. A hot camera generates noise, so turn the camera off if you're not using it. Also, turn off any features you don't need, including the flash. And don't be afraid to fill up the memory card (the camera’s image-storage media). The delete button is your friend for getting rid of unwanted images. In fact, the best thing about using a digital camera is that you can see the results immediately, know whether you're getting good images or not, and make adjustments accordingly.
Digital cameras capture auroral color as well as their film-based counterparts. This image was taken using a Sony DSC-F707 digital camera, an f/2.0 wide-angle lens, and a 30-second exposure at ISO 400. The bright star just above the trees is Arcturus.
Courtesy Paul Valleli.