Chris D.
Google
A ticket here covers all 3 Estates, the Stavanger museum, maritime museum & canning museum. It's not bad for 140 NOK ($€£13.50 apx). There is a bit of a walk here from the city center, about 15 minutes with modest uphill climb.
I would recommend going here as your start to the 3 Estates after visiting the maritime museum & Stavanger museum.