Polaris

Polaris (also known as the pole star or the North Star) was a star visible from Earth in the constellation of Ursa Minor. Ian Chesterton once showed it to Vicki Pallister in 64 (PROSE: Byzantium!) and again to Barbara Wright shortly after leaving that year. (PROSE: The Eleventh Tiger)

In 1699, Captain Henry Avery explained to the Eleventh Doctor that he used the North Star to navigate his ship. (TV: The Curse of the Black Spot)

In 1807, when she discovered her compass wasn't working, Madam Ching tried to use the stars to navigate, pointing out Polaris and Ursa Minor, but this too soon proved unworkable due to the Sea Devils' disruptions to the planet's orbit and magnetism causing the stars to appear to shift around in the sky. (TV: Legend of the Sea Devils)