Can anyone share experiences with shooting large format film star trail shots? I'm planning for a shot that involves star trails as one component and I'm planning on shooting with large format film (or possibly 6x17 as an alternative). I've been told that over time temperature changes can cause the film to move through the exposure? I have a dew not that I was planning to use to heat the lens to keep dew off. Do I need to extend this to the film back as well somehow? Any help will be greatly appreciated.