A star chart was a map that plotted out the locations of stars and allowed for points of reference in order to deal with navigation in space travel.
When John Crichton first arrived on Moya, he asked to see some star charts so that he could try to find some common points of reference with Zhaan and D'Argo. ("Premiere")
When Moya was forced to land on Denea, Crichton asked Lyneea if she had any star charts or deep space photographs in order to figure out where he was. ("I, E.T.")
When the crew explored the wreckage of the Zelbinion, Aeryn Sun and D'Argo found that the navigational consoles had been destroyed and no galactic star charts were available. ("PK Tech Girl")
On the New Moon of Delvia, Tahleen told Crichton that there were no star charts or reference points home to Delvia, because Delvians preferred to stay at home. ("Rhapsody in Blue")
When Crichton and Aeryn were looking at the stars, Crichton showed Aeryn a star chart he had created, naming all of the constellations. Aeryn pointed out that they already had names, but Crichton felt that "Huey, Louie, and Dewey" was a less boring name than Mintaka III. ("Green Eyed Monster")
As Moya neared the edge of Tormented Space, Pilot was hesitant to enter without reliable star charts and the traders were asking exorbitant prices for theirs. ("Twice Shy")
While negotiating with Emperor Staleek of the Scarrans, Crichton had Aeryn offer a navigational data chip with local star charts directing Staleek and Ahkna to a location of their choosing to demonstrate the wormhole technology. ("We're So Screwed - Hot to Katratzi")