head out to mount stromlo, its where the observatory is. high and away from city lights, just set up in the car park or side of road. watch out for cyclists, its a good ride for training. they do astronomy nights so jump on the website and see if any functions are scheduled or if the recommend a good safe setup site for you. not really many high places around canberra with unobstructed views. don't know if tidbinbilla car park is accessible or if they are amenable so could be worth contacting them to ask. either way high in canberra at night can mean cold and wind and getting out away from light pollution means watch out for roos when driving. I guess there is also lake george (big flat open nothingness) and what about asking bazza if you can visit his ASIGN II observatory and setup on his lawn?
avoid looking to the south east for a spot unless you want aircraft trails.