This astrolabe – shown here laid out in its constituent parts – was made in Isfahan in Iran by Hajji ‘Ali in 1793 (1208 AH) reviving an earlier tradition of beautiful craftsmanship (reflected not only in scientific instruments but in the art and architecture of Iran during the Safavid period of Iranian history).
An astrolabe is made up of a number of plates, each designed to be used in a particular latitude, with a marked grid to help the user find the direction of Mecca from a range of different locations. This makes it an ideal travelling instrument for devout Muslims. As the Islamic world expanded, calculations for the times of sunrise and sunset during Ramadan, prayer times and the direction of Mecca needed to be made, as they were no longer the same for everyone. The convenient and portable astrolabe made this possible.
In the top right hand corner of the main, central, disc (the mater) of the instrument shown here, you will see the grid that helped the user find the direction of Mecca. Also included on this densely decorated mater is a grid for working out trigonmetrical problems, a shadow square for finding the height of buildings, and various tables to allow the user to make astrological calculations and predictions.
Islam has never encouraged astrology, any more than Christianity has, but it was nonetheless a popular and an important driving force behind improvements in early astronomy, both in the Islamic world and in Europe, making measurements and predictions (about future positions of celestial bodies) more precise.
This is an early scientific instrument called an astrolabe. An astrolabe is both an observing tool – it has a moveable rule at the back with sights that you can use to find the height of stars, the Sun or even a building above the horizon – and a calculating tool. At its simplest it is can be used to calculate the time from the height of the Sun or a star, and to find their rising and setting times.
Many particularly Islamic astrolabes however also include tables for making all sorts of extra astronomical and mathematical calculations. This astrolabe was made in around 1230 AD (628 AH by the Muslim calendar) for a muezzin – the person who calls Muslims to prayer from the mosque.
The astrolabe was known, at least in theory, to the ancient Greeks, but it was within the Islamic world that it developed into a precision calculating instrument and essential tool for any astronomer. The astrolabe was used in the Islamic world, and later in Europe for many centuries, for everything from astronomy to surveying to time keeping. An adapted form was even used for navigation.
In Europe, from the 17th century onwards, its various uses were gradually replaced with the invention of the telescope, the theodolite, the pendulum clock and other such instruments. In the Islamic world, however, it continued to be prized for its versatility as a compact, multi-functional tool, and even today it is regarded by many as an icon of Islamic craftsmanship and ingenuity.