A Copernican armillary sphere with internal orrery. The asteroid belt and Mars, Jupiter, Saturn, Uranus and Neptune are represented by brass discs on curved quadrant arms. Earth and the Moon are represented by wooden spheres; their orbits and rotation are demonstrated with a geared metal armature. A central brass sphere represents the sun. The entire assembly is raised on a turned ebonized stand.
This is a Copernican armillary insofar as the instrument shows the sun at the center to the solar system, with the planets revolving around it. The discs representing the planetary orbits may be considered an internal orrery — an instrument which shows the proportional size and relative position of the planets, and times of their revolution. Another standard type of Copernican armillary represents the planets as concentric rings, rather than discs.
In 19th century France, armillary spheres served to demonstrate various theories of astronomy. Typically, they have some combination of concentric rings to indicate planetary orbits, the zodiac band of constellations, and terrestrial and celestial measurement circles such as the equator and the Tropics of Cancer and Capricorn, and solstice and equinox bands. Some, like this one, also contain an internal orrery.
A Copernican armillary sphere has a sun ball at the center, with planetary and zodiac armillary rings, demonstrating the modern theory of the solar system, first popularized by the Polish astronomer Nicolaus Copernicus (1473-1543) in his important treatise in which he proposed the revolutionary theory that the sun was the center of the universe, thereby challenging the geocentric theory of Ptolemy.
Condition: Generally very good, the metal with natural oxidation patina, with the usual overall wear, scratches, dings.