When I shot digital it was always ISO 100 for the northern lights to keep the noise down and I was still able to use 10-15 second exposures. The digital sensors seem to capture a lot more than the naked eye can see. Although someone like my friend David Cartier is shooting 800-1600 and his photos are incredible. I mean seriously incredible, if you want to see some of the best aurora photography anywhere go check out his Flickr stream.

I am not sure you could do it with 100 film although to be honest I have never tried. Even though a film Provia 100 has no reciprocity issues up to 1 minute exposures I am just not sure if it would be sensitive enough. It's worth trying but I would definitely plan on shooting some faster film as well. As you know once the exposures get too long the aurora can get kind of blurry. If I go out again I'll try pushing film to 800 and see how it goes.

All this technical info aside, the biggest reason my aurora photos are few and not the greatest is because it takes a lot of willingness to go out in the cold and stay up late and hope for the best and too often my warm bed tends to win out. If you are serious about the aurora take an afternoon nap, dress very warmly and get out away from the light pollution on any clear night and I'm sure you'll get some good stuff.

Also please let us know how it goes for you on your trip!