The Planisphaerium is a work by Ptolemy. The title can be translated as "celestial plane" or "star chart". In this work Ptolemy explored the mathematics of mapping figures inscribed in the celestial sphere onto a plane by what is now known as stereographic projection. This method of projection preserves the properties of circles.
Publication
Originally written in
Ancient Greek,
Planisphaerium was one of many scientific works which survived from antiquity in
Arabic translation. One reason why
Planisphaerium attracted interest was that stereographic projection was the mathematical basis of the
plane astrolabe, an instrument which was widely used in the medieval Islamic world. The
Suda lists a work of Ptolemy titled
Simplification of the Sphere () which is presumed to be
Planisphaerium. In 1143 the work was translated from Arabic into Latin by Herman of Carinthia, who also translated commentaries by Maslamah Ibn Ahmad al-Majriti.
The oldest known translation is in Arabic done by an unknown scholar as part of the Translation Movement in
Baghdad.
Planisphere
The word planisphere (Latin planisphaerium) was originally used in the second century by Ptolemy to describe the representation of a spherical Earth by a map drawn in the plane.
[Journal of the British Astronomical Association
yr:1995 pg:35]
Editions and translations
External links
