I activated this summit as I was travelling through the region in mid April 2022. I had never visited the site before.
The site is closed to visitors by a boom gate about 400m down from the visitor centre. The opening hours when I was there were 10am to 4pm (or 4:30?) on specific days of the week, not including all regular business days. Some of the restrictions were implemented due to Covid 19 in 2020/21/22. Before driving out there to visit it I recommend consulting the website for Siding Spring observatory.
It is easy enough to find. From the clocktower roundabout in Coonabarabran, head west, negotiate a few roads within the town and then head out to the west for about 20 km, where the observatory road is well sign posted. A winding and sometimes steep trip of several km takes you up to the boom gate, and if you arrive during visiting hours the gate will be open and you can drive up to the visitor centre carpark. The observatory itself is visible on the hilltop at times during the approach, even from the lower road.
A SOTA activator will notice many prominent hills in the area. Some are SOTA summits themselves but not all.
At this SOTA summit, your only option for activations is to set up near to the visitor centre as all roads leading past that to the observatory are signposted as restricted to staff and authorised visitors. Looking at my Garmin GPS it appeared that much of the parking area and the nearby grassy areas next to the fence were within the AZ. There are several picnic tables which could be used. But my advice is to check it yourself to be sure you are following the sota rules. I followed my usual pattern of putting a tarp on the grass and setting up everything on that. I tied the pole to a fence post.
After logging a reasonable number of contacts on both SSB and CW on several HF bands, I packed it all up and returned it to the car. I then went into the visitor centre and enjoyed a coffee from the cafe there. Staff were keen to offer me a guided tour of the observatory, but I didn’t have the time for that and told them I would do that on my next visit.
The site was chosen for the observatory for its remoteness and lack of optical interference, and came to greater importance for the university (ANU) after the destruction of the Mt Stromlo observatory by the 2003 bushfires. Following the decision to focus on Siding Spring, the ACT Government went ahead with previously shelved plans to develop areas near Mt Stromlo for residential suburbs, which now nestle in the foothills of Mt Stromlo, in particular on the northern side. The previously opposed development along the north side of Duffy has gone ahead also. So optical observations from Stromlo are now completely off the table.