Astrophotography anyone?

I want to try astrophotography!  We have a good camera for it and I think I just found a great location, Grassland Mountain Observatory in Madison County. Unfortunately, it is privately owned and permission is required to go there.  Here are directions.  On the weather report, dark blue is good.  This site is frequently used by the Astronomy Club of Asheville.  I think I should use the following setup:

- Manfrotto tripod
- Sony camera
- 24 mm lens
- shutter speed of below 20 seconds (based on 500 / lens in mm [24 in my case])
- RAW files
- ISO of 1600 - 3200

Has anyone done this?