Taking photos of the northern lights at 3 am from a small boat at anchor is tricky.  There is always a little movement even the sea was calm.  It was almost completely dark.  I mounted my Nikon D4 on the tripod and cranked up the ISO to 6400 and used a focal length of 24mm.  In order to minimize the length of the exposure, I set the Aperture to 2.8 which gives me zero depth of field.  So, how do you focus? I barely could see a ridgeline of a hill.  I pointed the camera to the hill and tried to set the autofocus sensor on the line, focused by using back focus, and re-composed.  The exposure was ½ a second.  Shooting in RAW format gave me more flexibility in post developing and I was able to bring out the northern lights as well as some of my surroundings.  I reduced the digital noise with NIK Define.

Northern Light photo after processing

Northern Light photo without processing