Planisphere

In astronomy, a planisphere is a projection of the celestial sphere onto a plane. Because of the projection, certain parts of the celestial sphere cannot be shown. Hipparchus discovered that it was possible to do a projection which keeps the angles intact.

Planisphere Media

Philips' Planisphere, ca. 1900
Medieval planisphere, c. 1000. National Library of Wales MS 735C, Aberystwyth.

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