page_title: Armillary sphere
section_title: Medieval Middle East and Europe
hierarchical_section_title: Armillary sphere / History / Medieval Middle East and Europe
context_page_description: An armillary sphere is a model of objects in the sky, consisting of a spherical framework of rings, centred on Earth or the Sun, that represent lines of celestial longitude and latitude and other astronomically important features, such as the ecliptic. As such, it differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations. It was invented separately in ancient Greece and ancient China, with later use in the Islamic world and Medieval Europe.
  With the Earth as center, an armillary sphere is known as Ptolemaic. With the Sun as center, it is known as Copernican.
  The flag of Portugal features an armillary sphere. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration. In the flag of the Empire of Brazil, the armillary sphere is also featured.
context_section_description: Persian and Arab astronomers produced an improved version of the Greek armillary sphere in the 8th century, and wrote about it in the treatise of Dhat al-Halaq or The instrument with the rings by the Persian astronomer Fazari (d.c. 777). Abbas Ibn Firnas (d.887) is thought to have produced another instrument with rings (armillary sphere) in the 9th century which he gave to Caliph Muhammad I (ruled 852–886). The spherical astrolabe, a variation of both the astrolabe and the armillary sphere, was invented during the Middle Ages in the Middle East. About 550 AD, Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant treatise on the instrument. The earliest description of the spherical astrolabe dates back to the Persian astronomer Nayrizi (fl. 892–902). Muslim astronomers also independently invented the celestial globe, which were used primarily for solving problems in celestial astronomy. Today, 126 such instruments remain worldwide, the oldest from the 11th century. The altitude of the sun, or the Right Ascension and Declination of stars could be calculated with these by inputting the location of the observer on the meridian ring of the globe.
  The armillary sphere was reintroduced to Western Europe via Al-Andalus in the late 10th century with the efforts of Gerbert d'Aurillac, the later Pope Sylvester II (r. 999–1003). Pope Sylvester II applied the use of sighting tubes with his armillary sphere in order to fix the position of the pole star and record measurements for the tropics and equator.
caption: An armillary sphere in a painting by Florentine Italian artist Sandro Botticelli, c. 1480.
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