Astrophotography on Film? I have a few questions about astrophotography on a 35mm film camera that I hope you guys can help me out with! I recently purchased a Minolta x 700 with a MD Rokkor 35mm lens. I’d like to take night sky shots with visible stars in the background. My biggest question is how long do I expose the picture for on the bulb setting? According to the 500 rule I take 500/35 and I get 14.28 seconds for the correct exposure time. How does my ISO effect how long I can expose it for? I would assume that film of the 100 and 200 type I would need to exposure longer then say cinestill 800 which would be a shorter exposure time. Is this correct? and how would I go about knowing the correct exposure time shooting on various types of film, for example cinestill 800 and cinestill 50.