The basic idea is very simple, just take a sequence of images that capture enough light in each image and then play them back at anywhere between 15 to 30 frames per second - so you end up with a speed up time reality movie of that night. To do this you are best to have a lens that gathers light very quickly (atleast f/2.8, even wider is better) and a camera that performs well when used at high ISO's.
In this example I am using a 24mm f/1.4 lens with a 20 second exposure ISO 3200 - with the drive on the camera set to continuous and then a basic on/off type remote keeping the camera on all night, when used in this way the camera will just keep taking photo after photo until either: your battery goes flat, the memory card space runs out, or you turn the camera off. looking East over Lake Tekapo as the center of our milkyway rises