Al-Ṣāghānī

  • Boris A. Rosenfeld
Living reference work entry
DOI: https://doi.org/10.1007/978-94-007-3934-5_9305-2

Abū ḥāmid Aḥmad ibn Muḥammad al-Ṣāghānī al-Asṭurlābī was an Arabic astronomer and mathematician. He was born in Chagaian (Central Asia) and worked in Baghdad.

His main work was the Kitāb fī’l-tasṭīh al-tāmm(Book of the Perfect Projection on to a Plane) which is extant in two manuscripts. The treatise is devoted to a generalization of the stereographic projection of a sphere onto a plane, usually used in the making of astrolabes. This concerns the projection from a pole of the sphere onto the equatorial plane or a plane parallel to it. Under this projection, circles on the sphere are imaged onto the plane as circles or straight lines. The “perfect projection” invented by al-Ṣāghānī is the projection of the sphere from any point of its axis onto a plane orthogonal to the axis. Under this projection, circles on the sphere are imaged on the plane as conic sections (ellipses, hyperbolas, and parabolas) or straight lines. These descriptions of methods for conics construction are important...

Keywords

Line Produce Equatorial Plane Construction Method Mathematical Treatise Stereographic Projection 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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References

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Boris A. Rosenfeld
    • 1
  1. 1.State CollegePAUSA