[Ingo]

How should I set the white balance for a night sky? I know during normal photography I use a gray card, but I don't think that'd work for the night sky. Should I just leave it on auto?

Also, whenever I use my 24-70mm at say 15 seconds exposure, it always comes out extremely overexposed at F2.8, is it because of the light pollution? Staring straight up, it's pretty dark which is where I position my camera, but towards the horizons, there's a lot of light pollution. I still get overexposure at 24mm and 15 seconds exposure.