Although the astrolabe has origins registered more than 1,500 years ago, it was highly developed in the Islamic world by 800 and was introduced to Europe from Islamic Spain (Andalusia) in the early 12th century. It was the most popular astronomical instrument until about 1650, when it was replaced by more specialized and precise instruments. Astrolabes are still appreciated for their unique abilities and their value for astronomy education
What is an Astrolabe?
The astrolabe is an astronomical computer for solving problems related to time and the position of the sun and stars in the sky. Various types of astrolabes were made. By far, the most popular type is the planispheric astrolabe, in which the celestial sphere is projected on the plane of the equator. A typical ancient astrolabe was made of brass and was about 6 inches (15 cm) in diameter, although they were made large and small.
Astrolabes are used to show how the sky looks at a specific place at a given time. This is done by drawing the sky on the face of the astrolabe and marking it so that positions in the sky are easy to find. To use an astrolabe, you adjust the moving components for a specific date and time. Once defined, the entire sky, visible and invisible, is represented on the face of the instrument. This allows many astronomical problems to be solved in a very visual way. Typical uses of the astrolabe include finding time during the day or night, finding the time for a celestial event such as sunrise or sunset and as an accessible reference to celestial positions.
Astrolabes were also one of the basic tools of astronomy education in the late Middle Ages. Ancient instruments were also used for astrological purposes. The typical astrolabe was not a navigation instrument, although an instrument called the sailor’s astrolabe was widely used. The sailor’s astrolabe is simply a ring marked in degrees to measure celestial altitudes.