A star chart, also known as a star map, is a map of the night sky that astronomers use to identify and locate astronomical objects such as stars, constellations, galaxies and planets. It is a fundamental tool in celestial navigation and has been used since ancient times to aid in the understanding and organization of the cosmos.
A star chart represents the positions of the stars as they appear from Earth. The chart is usually a two-dimensional projection of the celestial sphere, which is an imaginary sphere surrounding the Earth onto which all celestial bodies are projected.