As Paul mentioned, this Saturday Parramatta Park is hosting a Star Gazing Night. Talks will include the incomparable David Malin. For more information click on events at the PPT Website.
http://www.ppt.nsw.gov.au/
I've also included a Parramatta Park map. Close access to the various events is through the Pitt Street gate. The park itself will be vehicle free for the evening.
Best regards,
Sharonr :-)