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.