How to Photograph the Northern Lights
OK, so you want to photograph some aurora?
WHAT YOU NEED
First of all you need the aurora to be actually active in your area. There are plenty of ways to check this online, I use a few different apps and websites, I find Softserve News very good. Obviously the further north you are the better chance you have but I recommend becoming familiar with the KP index, this is a number of lines from north to south which measures the latitude of aurora visibility. For example, here on the Isle of Lewis, a KP 5 level of activity should be decently visible, further south you want to see KP 6-8. You will also need some clear skies to the north.
Second up your of course going to need a camera. Any camera capable of exposures up to 30 seconds or more can capture the dancing lights but the better the camera and lens, the more capable it will be to handle low light photography. I currently use a Canon 5Dmk3 which is great for low light and I can safely bump up the ISO without compromising the image quality.
Your also going to need a tripod, your going to be shooting long exposures and there's absolutely no chance you can do it handheld. You might also want a remote shutter release or a timer to further reduce any shake.
Once you have your camera in position your going to want to dial in your manual settings, auto just isn't going to cut it here I'm afraid.. These will vary from night to night and different levels of aurora. I tend to start with my lens at its widest aperture (f2.8 on my Samyang 14mm), a shutter speed of 15-20 seconds and my ISO set to 800. After reviewing, if the image is too dark I can alter it by extending the shutter speed or bumping up the ISO, too bright, reduce shutter speed or lower ISO. Ideally you want to keep the shutter speed below 30 seconds, after that you will start getting blurred aurora and you will also start to see star trails caused by the Earths rotation.
Other than that, there is NO RULEBOOK! You just have to get out there and do it your way, the more you shoot, the better you will become.