Armillary Sphere

Instrument used by ancient astronomers composed of rings to represent the Celestial Equator, The Tropics, the Ecliptic, Horizon and Meridian. De Vore has the inventor as Eratosthenes, Larousse as Thales or Anaximander. In any event, an armillary sphere is constructed with bands representing circles on the celestial sphere, connected along their diameters but free otherwise to rotate about each other to represent all the possible orientations of circles within a sphere.