Hey all, This question has been on my mind for a while, and tomorrow I will start a two day camping trip in Egypt's White/Black Desert. I know it will be dark at night but I want to take photos of the camp/campfire and possibly star formations etc. Sometimes when I shoot with long shutter speeds my camera indicates that 30 seconds is not enough (the max I can go on my D90). I know how the bulb function works but I do not know how to calculate how long the shutter should be. Any thoughts? ..I will have a tripod and a remote with me.