My wife and I are taking a trip to the Arctic Circle soon, hoping (but not presuming) to see the Northern Lights. I'm taking my Mamiya 7ii + 80 + 65, and possibly the 150. I plan to use Velvia 100 and Provia 400X. And a tripod. Any advice on capturing the Lights with this kit would be welcome: exposure times, aperture, film, etc. We may never see them, but if we do, I'd like to record it as well as I can. Many thanks.