Somewhere between a 20 and 30 second exposure. I went out shooting last Thursday night with Mike from MikesRightBrain. We took some shots around the south end of Lincoln Park and North Avenue Beach. My shutter release cord stopped working halfway through or so, so I had to hold down the shutter and try not to shake the camera/tripod for half of the night. This is one of the shots that was a result of me holding the shutter open with my finger. Most of them turned out pretty well actually, just a bit of a pain. Next time I'm going to plan ahead and always carry 2 with me.