Origins of Astrolabe theory

The origins of the astrolabe were in classical Greece (astro-star and labe(labium) the one who search) and thus astrolabe is the one who search for stars. Appollonius (225 BC) was the great codifier of conic sections, probably studied the astrolabe projection. The most influential individual on the theory of the astrolabe projection was Hipparchus who was born in Nicaea in Asia Minor about 180 BC but studied and worked on the island of Rhodes. Hipparchus, who also discovered the precession of the equinoxes and was influential in the development of trigonometry, redefined and formalized the projection as a method for solving complex astronomical problems without spherical trigonometry  and probably proved its main characteristics. Hipparchus did not invent the astrolabe but he did refine the projection theory.

The first major writer on the projection was the famous Claudius Ptolomy (150 AC) who wrote extensively on it, in his work known as the Planisphaerium. There are tantalizing hints in Ptolomy’s writing that he may have had and instrument that could justifiable be called an astrolabe. Ptolomy also refined the fundamental geometry of the Earth –Sun system that is used  to design astrolabes.

The Astrolabe in Europe

The earliest astrolabes used in Europe were imported from Moslem Spain with Latin words engraved alongside the original Arabic. It is likely that these imported  astrolabes influenced European use of Arabic star names. By the end of the 12th century there were at least a half dozen competent astrolabe treatises in Latin, and there were hundreds available only a century later. Europeans makers extended the plate engravings to include astrological information and adopted the various timekeeping variations used in that time.

The astrolabe was widely used in Europe in the late Middle ages and Renaissance, peaking in popularity in the 15th and 16th centuries, and was one of the basic astronomical education tools. Knowledge of astronomy was considered to be fundamental in education ans skill in the use of the astrolabe was a sign of proper breeding and education. Their primary use was, however, astrological. Geoffry Chaucer thought it was important for his son to understand how to use an astrolabe, and his 1391 treatise on the astrolabe demonstrates a high level of astronomical knowledge.

Astrolabe manufacturing was centered in Augsburg and Nuremberg in Germany in the 15th century with some production in France. In the sixteenth century, the best instruments came from Louvain in Belgium. By the middle of the seventeenth century astrolabes were made all over Europe. George Hartmann in Nuremberg founded a particularly interesting workshop in about 1525. He used a early form of mass production to produce his high quality instruments. Brass astrolabes were quite expensive, and only the wealthy could afford a good one. Paper astrolabes (as the Antiquus one) became available as printing developes, and many were surely made, although few survive.

Several interesting astrolabe variations known as Universal astrolabes which make a single instrument usable in all latitudes were invented in the 15th and 16th centuries, but due to their high cost and complex operation, never gained the popularity of the planispheric type. These instruments projected the celestial sphere on the equinoctial colure and lacked the intuitive appeal of the planispheric type.

A Derivate of the circular astrolabe is reduced to a quadrant was described in 1288 by Profiat Tibbon de Montpelier. Few examples of astrolabe quadrants, commonly called the quadrant novus (new quadrant) survive, but many treatises on its construction and use were published . A form of astrolabe quadrant was quite popular in the Ottoman Empire until the early XXth century. Several quadrants using the stereographic projection were introduced in the 17th century. The most popular was devised by Edmund Gunter (1581-1626) in 1618. Gunter’s quadrant was quite easy to use in comparison to the older quadrants novus and become widely used.