How to shoot Northern Light
Camera: Although it’s possible to photograph the Northern Light with a mobile phone, it’s easier with a DSLR or mirrorless digital camera.
Lens: Most prefer to use a wide-angle lens around 15-28 mm
Tripod: You need a tripod
Remote trigger: Optional. It’s also possible to use the self timer
The Northern Light moves all the time, and it has to be dark when you shoot. That means that you have to use quite a long exposure time and a tripod to catch it.
Mount the camera on the tripod and compose the image. Chose to shoot with the lens wide open and choose an ISO setting between 800-3200, depending on how fast your lens is, how dark it is, and the nature of the Northern Light. The exposure time is the most important – choose as short exposure time as possible!
If you choose too long exposure time when the Northern Light is active, you lose definition and spreads all over the image. Optimal, you want to catch these beautiful windings, not a green “slime” without a definition covering all the sky.
Earth Rotation and the 400-rule
The earth rotates once every 23 hours and 56 minutes. That has relevance for long exposure photography in that you will get star trailing in the images when the exposure time gets too long. What is too long?
A useful way to calculate that is to use the 400-rule. Divide the lens focal length with 400, and you get the maximal exposure time in seconds that you can use before you get star trailing in the image.
With a 15 mm wide-angle lens, you can use 400/15=26,67 (27 seconds)
To be safe – stay a couple of seconds under these maximal values.
Some useful tips
A beginner is often very focused on the Northern Light in itself. Try to compose the image to create an exciting result! Northern light reflected in water could be stunning, for example. Or try to put an object in the foreground.
I would also recommend shooting in raw format, so you have greater opportunities to do some postproduction.