Planispheres

Refers to images depicted on a flat surface, but representing the celestial sphere, which is the stars and constellations as they are located on the apparent hollow sphere of the sky as seen from the surface of the Earth. They appeared in Europe around 1515, though simple depictions of constellations had been known since the time of ancient Egypt. They are a narrower concept to "astronomical charts" because "planispheres" are specifically early depictions of the heavens on a flat surface, where the concept being depicted is of a sphere projected on a flat plane; "astronomical charts" may refer to charts from a much wider historical range, and do not necessarily refer only to charts where the heavens were conceptually considered to exist on or in a sphere. For representations of the heavens actually depicted on a sphere, as opposed to being projected on a flat plane, use "celestial globes."