The Battlestar search challenge in Fortnite week 9 is called “Follow the treasure map found in Moisty Mire”. The treasure map found in Moisty Mires shows a house with two chimneys above a triangle of trees.
These two locations for the week 9 treasure hunt can be found south of retail row. To find the treasure / battlestar, you need to get on top of the house that the Moisty Mire treasure map leaads you. The battlestar is located on top of the chimneys.