Key to succesful northern lights shot are the correct camera settings of aperture (f-stop), shutterspeed and ISO sensitivity. The right exposure is the most important thing. Under exposed picture is too black and over exposed too white. In northern lights photography it is essential to use fast objective and expose the shot longer than usual. Too high ISO sensitivity will make the picture grainy.
Aperture controls the brightness of the image and the amount of light passed on to sensor
ISO controls the sensitivity of the sensor, higher ISO introduces grain to image
Exposure time controls the amount of light passed on to sensor, our camera is on a tripod to allow for longer exposures