Monday, September 09, 2013

Stolen and Found

Recently in Amsterdam the Swedish museum recovered a rare 1590 astrolabe. An astrolabes is a devise used by astronomers, navigators and astrologers to locate the positions of the sun, moon, planets, and stars to determine local time, for surveying, and casting horoscopes. Astrolabes were used as early as the 150 B.C. until about 1650 A.D.

The brass-and-silver astrolabe, made in 1590 and worth about $750,000 has been missing from the Swedish Museum for almost fifteen years. It turned up when an Italian collector discovered that the piece was listed as missing and came forward to return it.

The astrolabe is a very ancient astronomical computer for solving problems relating to time and the position of the sun and stars in the sky. Several types of astrolabes have been made. By far the most popular type is the planispheric (a map of a sphere) astrolabe, on which a map of the stars and planets are shown. A typical old astrolabe was made of brass and was about 6 inches (15 cm) in diameter, although much larger and smaller ones were made.

Astrolabes are used to show how the sky looks at a specific place at a given time. Made up of several disks engraved with critical information, the disks are adjusted to a specific time and date. Once set, much of the sky is represented on the face of the instrument. The back of the instrument was engraved with a wide variety of scales for measuring angles and determining the sun’s longitude for any date. Some astrolabes included a scale for solving trigonometry problems (shadow square). A cotangent scale was added to many
Islamic instruments to determine prayer times as well as the true direction to Mecca.

The Swedish Museum (Skokloster Castle) in Stockholm, is glad to get the piece back. The astrolabe was stolen in 1999, one of a string of unexplained thefts of books and objects at the castle. Other precious items, dozens of manuscripts were noted as missing from the Royal Library in 2004.
This newly found astrolabe is in outstanding condition and could still be used today. It is an intricate mix of astronomical knowledge and metal craftsmanship, the piece is about the size of a pancake, and engraved with the name of its builder, Martinus Weiler.

German scholar Petra Schmidl of Bonn University, who studies astrolabes, described astrolabes as a “two-dimensional model of the three-dimensional world.” She goes on to say that modern clocks, while precise, tend to leave our understanding of time “stripped from its astronomical origins. Before telescopes, the astrolabe was the way you could say: ‘What time does the sun rise? When will it set?” Today fewer than 2,000 astrolabes survive.
For more information see the full article from the Washington Post.

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