Jan Van der Straet, ‘Astrolabium’ (detail). Antwerp, 16th century. FM: 22.I.8 © Fitzwilliam Museum, University of Cambridge.

Astrolabes are attested as far back as classical antiquity.

This image, designed by the Flemish artist Jan Van der Straet (or Stradanus, as he is more commonly known) depicts the Florentine explorer Amerigo Vespucci (1455-1512) locating the constellation called the Southern Cross. It is night time, and his companions seem not to have been able to stay awake, but Vespucci stands in the centre, holding up a compass and a spherical astrolabe - the tool celebrated in the title of the image.

A second astrolabe sits on the impromptu desk in front of Vespucci. The complex ingenuity of Renaissance astrolabes enabled their users to identify stars and planets, and to measure their positions and movements. The image emphasises the dual function of this process. On the one hand, the very shape of the Southern Cross gives it Christian significance, an association reinforced by the model of a crucified Christ on Vespucci’s desk. On the other hand, the ships in the background and the boat in the foreground signal the practical utility of astronomy for navigation, and thus for global exploration and international trade.

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Left: Georg Hartmann, Astrolabe. Nuremburg, 1532. © The Trustees of the British Museum, CC BY-NC-SA 4.0. Right: Georg Hartmann, Paper Astrolabe. Nuremburg, 1542. Inv. 49296 © History of Science Museum, University of Oxford.

The astrolabe was an early scientific device, consisting of a two-dimensional model of the celestial sphere, used primarily for calculating astronomical measurements, but put to a variety of uses in navigation, astrology and philosophy. Taking their name from a Greek word meaning ‘star-taker’, astrolabes are attested as far back as classical antiquity. They were developed to a high level of technical sophistication during the Islamic Golden Age, and were used both in astronomy and for determining the direction of Mecca. From the Islamic world, they were transmitted to medieval Western Europe, where they continued to be used until the end of the seventeenth century.

Producing astrolabes required a great deal of skill, and the end results are works of art as well as of technical mastery. Georg Hartmann seems to have been the first to introduce standardised parts for his brass astrolabes. This meant that the parts could be ‘mass-produced’ and then assembled, presumably lowering costs.

Even so, brass astrolabes would have been very expensive, and cheaper alternatives were available. The second example, also produced by Hartmann, is constructed primarily of paper and wood. The practical utility of the astrolabe meant that it was in widespread use across a variety of spaces, from the study to the ship, and prompted innovations in production and design techniques which increased access to cosmographical knowledge.

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