Scott just adding a little to Allan's comments, here is a link to some information on Bretti Reserve (which is managed by Gloucester Council).
http://www.findacamp.com.au/camp-site.php?camp=605
You can find more information on the Net by just doing a search on 'Bretti Reserve'.
It sits at the junction of two small rivers, so there is plenty of water around for showers (but you cannot drink it - so bring your own drinking water).
It is a popular 'Free Campground' and thus is on the Grey Nomad circuit and there are always a few caravans positioned at spots down by the river. We usually try to setup at the far end from the entry road on a flat spot just east of the green toilet shed.
As Allan indicated it is one of the darkest places we have found so far, and its better than Chaffey Dam up near Nundle.
Just one word of warning: It is a popular spot for family camping during the school holidays and can get crowded during that period. Large groups from Newcastle, and other places sometimes setup there during the holiday period and can be noisy. However, its a very big area and it is usually possible to get away from them, and Bretti Heights was used during the September School holiday period last year (which corresponded with the New Moon). Bretti Heights is the first ridge above the valley floor to the south of the main camping area. It's a little further to walk to the toilets but that is one factor that makes it usually available. There is a flat top area on the ridge that is fine for camping, but bring a shovel - the reason being that cows occasionally are allowed to graze on the reserve (not during the holiday period that I know of) and the little piles they leave behind might need to be moved from your camp area.
Finally, power; there is no electricity at Bretti, which is part of it's charm in my book; but this means you need to be self-sufficient in power, whether its batteries or a generator or solar panels etc. If your going to be running your scope all night, especially if imaging, you need to know how much power you will need. Obviously running generators late at night is not a good idea for your neighbors but during the day and early evening they are fine (especially when you can shroud them in some way).
If you have a caravan your taking along there is plenty of flat area on the valley floor, but up on the ridge there is less space for caravans but I have seen them up there.
Looking forward to seeing you there. Remember NSW School Holidays does not finish until Sunday the 19th, so if you go earlier expect it to be busy. After mid-day on the 19th they will be leaving and it will revert to the quite spot we all like so much.
You can probably meet up with someone heading up there on that day so following them is an easy option to finding the place and the access road. It's paved all the way down the hill to the valey floor and then gravel and dirt for a few hundred metres across the valley floor.
I may not get there until Monday the 20th as I have a family function on Sunday in Sydney but there will be others there on the 19th I believe (Ulrich will be I think).
