The Aurora here was captured in a single exposure at 12,500 ISO with with my Nikon D800, after some noise reduction in RAW and post. The sky exposure was 1.5 seconds, which is needed to maintain good texture in a rapidly changing and booming show like this. The foreground is a focus-stack of 4 images all at f/2.8, ISO 6400 and 2 minutes each. It ended up being so green because of all the reflected light being the only light source, I had to desaturate it about 60% just to look even a little natural to me! Obviously, I would have preferred a 1 second shot here for better water texture too, but we don't have ISO 200,000 yet!
Thanks for any comments you may have.