a model of the ancient celestial sphere used to fix the positions of heavenly bodies
an ancient instrument made up of rings around a sphere, depicting the relative positions of important circles of the celestial sphere
a skeletal celestial globe used to represent and study the movements of the planets
a skeletal celestial sphere with a model of the Earth or, later, of the Sun placed in the center
A model of the universe, consisting of a skeleton globe with metal rings. The centre of the globe represents the Earth, and the rings represent the horizon, equator and tropics. It was used to teach a particular kind of astronomy called spherical astronomy.
A type of spherical sundial.
set of rings corresponding to the circles of the celestial sphere, see article on the armillary sphere.
An armillary sphere (variations known as a spherical astrolabe, armilla, or armil) is a model of the celestial sphere, invented by Eratosthenes in 255 BC. Its name comes from the Latin armilla (circle, bracelet), since it has a skeleton made of graduated metal circles linking the poles and representing the equator, the ecliptic, meridians and parallels. Usually a ball representing the Earth or, later, the Sun is placed in its center.
