German armillary sphere, 1553

Armillary Sphere; brass, 5 1/2-inches diameter on small turned painted wooden stand. Overall height just less than 8 inches. Inscribed on tropic of cancer: "Caspar Vopelius Mathe. Professor Ubiorum Coloniae Hanc Sphaeram Faciebat Anno. 1553". Earth represented by brass ball at centre; four movable circles for Moon, Sun, Jupiter and Saturn.

Made by Caspar Vopel in Cologne, Germany in 1522, this brass armillary sphere has a turned wooden stand. A broad band, finely engraved with the star patterns of the Zodiac encircles the instrument. The armillary sphere is a demonstration device to explain the movements of the Sun, Moon, stars and planets across the sky. Its interlocking rings can be used to teach astronomical principles in same manner as a celestial globe or act as a model the universe. Based on the premise of an Earth centred universe, the armillary sphere was modified in the seventeenth century to teach the theory that the Earth orbits the Sun.