I've just got back from camping in Terrick Terrick NP and I must say it is a beautiful place. However, there are lots of trees and I didn't see anywhere open enough for astronomy. That said, I didn't get up to the north of the park so there might be something up there. The other option, not really, would be to set up right on top of Mt. Terrick, which is a large granite out crop. Getting your stuff up there would be hard though and the wind was strong enough to allow my dad and I to lean almost 45 degrees into it
. I can't say what the skys are like because it was never clear when I was there.