The Mechanised Celestial Globe by Jost Bürgi

Jost Bürgi, or Joost, or Jobst Bürgi (February 28, 1552, Lichtensteig, Switzerland – January 31, 1632), active primarily at the courts in Kassel and Prague, was a Swiss clockmaker, a maker of astronomical instruments and a mathematician.

The maxi card and the stamp on it with the nice appropriate postmark displays one of Jost Burgi’s most famous creations, The Mechanised Celestial Globe, made 1594 in Kassel, now atSchweizerisches Landesmuseum in Zurich.

In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with a particular celestial body. All objects in the observer's sky can be thought of as projected upon the inside surface of the celestial sphere, as if it were the underside of a dome or a hemispherical screen. The celestial sphere is a practical tool for spherical astronomy, allowing observers to plot positions of objects in the sky when their distances are unknown or unimportant.

Thank you Merja.