Star chart

Star charts were astronomical maps of constellations.

Voyager owned star charts that showed how to access "the dimension of death". These were tattooed onto the body of Astrolabus who then ran away. Considering them stole, Voyager instructed the Sixth Doctor to reclaim them. He eventually caught up with Astrolabus and Voyager killed him. (DWM: Voyager, Once Upon a Time Lord)