Use a tripod and manual control for everything (focus, aperture, and exposure time)--the automation will not work in the dark.
For terrestrial night photography, just use the above and:
* shoot a range of exposures
* shoot RAW for the greater dynamic range
* be very careful to minimize vibration (use a remote release, mirror lockup, and a delayed shutter)
For astrophotography:
* Exposure time is limited by the earth's rotation--a rule of thumb is to use a maximum of n/FL seconds where n is between ~150 and ~600 (depends on the camera, the lens and the desired sharpness). You can use longer exposures near the poles. If the exposure is longer, the stars will streak. (Of course, an exposure of hours will result in intentional star streaks.)
* You can use FLs from your widest wide angle to your longest telephotos.
* Use the largest apertures (unless you need to stop down to reduce lens aberrations).*
* Shoot a range of exposures--you cannot tell what you have until you see it on a big screen.
* Shoot RAW for the larger dynamic range.
* be very careful to minimize vibration (use a remote release, mirror lockup, and a delayed shutter)
The above will work for brighter objects--the moon, planets out to Saturn, constellations, and stars (perhaps you can resolve some double stars with a telephoto). You might even have a chance of imaging the M42 nebula (the middle "star" of Orion's sword). (You can see a bit of the nebula with binocs.)
The next step requires a motorized tracking drive to compensate for the earth's rotation. Then you start shooting multiple sub-exposures and combining them on the computer...
There is a nice tutorial on fixed tripod astrophotography at
http://www.bobatkins.com/photography...otography.html
Two samples shot from my backyard using a DSLR and a 400mm lens on a tracking mount: the M 31 Andromeda Nebula (100 min total exposure) and the M 42 Orion Nebula (26 min total exposure):
Doug