An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and vice-versa, surveying, triangulation, and to cast horoscopes. It was used in classical antiquity, the Islamic Golden Age, the European Middle Ages and Renaissance for all these purposes. In the Islamic world, it was also used to calculate the Qibla and to find the times for Salat, prayers.

The history of the astrolabe begins more than two thousand years ago. The principles of the astrolabe projection were known before 150 B.C., and true astrolabes were made before A.D. 400. The astrolabe was highly developed in the Islamic world by 800 and was introduced to Europe from Islamic Spain (al-Andalus) in the early 12th century. It was the most popular astronomical instrument until about 1650, when it was replaced by more specialized and accurate instruments. Astrolabes are still appreciated for their unique capabilities and their value for astronomy education.

Click on the images to see the dates when these astrolabes were made, and the places where they were found.


Roman Ribbed Glass Bowl, 1st Century AD

The first examples of ribbed bowls date back to the second quarter of the 1st century BC; from the middle of that century, the shape suffered a minor variation, with the adoption of a flatter or slightly convex bottom, which made the vessel more stable. Their production increased considerably from the late Hellenistic period on and continued during the 1st century of the Empire with a very elaborate typology and various dimensions. The most common colors were first orange-brown, aubergine and, more rarely, cobalt blue; these were gradually replaced by a simple transparent glass with light blue, dark or pale green reflections around the mid-1st century AD, when the taste for bright colors became old-fashioned. These bowls were largely used as tableware across the Mediterranean world, from Italy to the more western and northern colonies of the Empire, from the Aegean to the Levant. This wide distribution suggests that they were produced in Italian and Syro-Palestinian workshops.