[raymo]

The trick is to get as far from the city as possible, whilst getting the city
behind you, and not between you and your selected targets for the night.
So if you want to look to the west of a north /south line,I suggest that you drive up in the direction of Guilderton, and park near the coast, so that anywhere from SW to NE you are not looking over the city.
If you want to view to the east of a N/S line, I suggest that you drive up over Greenmount toward Northam so anywhere between N and S the city is behind you. To get skies dark enough for decent quality astrophotos you would have to go much further from the city.
raymo