Stars, landmarks on the Moon and Mars
- Apollo astronauts frequently aligned their spacecraft inertial navigation platforms and determined their positions relative to the Earth and Moon by sighting sets of stars with optical instruments. As a practical joke, the Apollo I crew named three of the stars in the Apollo catalog after themselves and introduced them into NASA documentation. Gamma Cassiopeiae became Navi – Ivan (Gus Grissom's middle name) spelled backwards. Iota Ursae Majoris became Dnoces – "Second" spelled backwards, for Edward H. White II. And Gamma Velorum became Regor – Roger (Chaffee) spelled backwards. These names quickly stuck after the Apollo I accident and were regularly used by later Apollo crews.