Welcome aboard
Crago in the Blue Mountains is semi dark and good enough for astrophotography. It can be tricky to park if it is busy and its quite rocky but is always open on the day advertised. Ilford (Wiruna) is very dark but its a good 2.5-3 hours from Sydney.
The Pony Club is about as dark as Crago (give or take a little bit) and is very comfortable, big open field and easy to get to. It can sometimes be off limits due to equestrian events so best to check on the forum before travelling. This shot was taken at the PC last Saturday in soft conditions.
http://farm9.staticflickr.com/8093/8...77e95ac3_k.jpg