expose to the right for the night sky

[rdking647]

5. the rule for avoiding star trails

600/effective focal length is the longest you can shoot without star trail. by effective focal length that depends on whether you have a crop sensor or a full frame.
for example a 50mm on a full frame means a 12 second exposure on a crop sensor 8 seconds.
some people use a rule of 500/focal length but ive found 600/focal length works pretty well especially if your not cropping.