Usturlab: The Navigator's Handbook of the Sky

Usturlap: The Explorer’s Handbook to the Sky 🧭

Hello, sky explorer! Have you ever looked up at the stars and wondered about their secrets? Or perhaps you’ve asked yourself, “What time is it?” and thought the answer might be found in the position of the Sun or the stars? The astrolabe is precisely that clever device from centuries ago — a circular instrument that allowed people to gather information about the sky long before computers or smartphones existed.

In essence, the astrolabe is a two-dimensional map of the sky. Just as a globe of the Earth can be flattened into a map, the astrolabe fits the entire sky into the palm of your hand. With it, people could solve many problems: determining the time, identifying seasons, and more. Let us take a closer look at this remarkable device.

The Sky in the Palm of Your Hand: How Does the Astrolabe Work? ⚙️

Using an astrolabe may seem like magic, but it is entirely grounded in science. Typically made of metals such as brass, the instrument consists of several stacked disks and movable parts. Its most fundamental components are the “body,” a engraved plate showing the sky for a specific latitude, and the “spider,” a network of lines marking the positions of stars.

To measure the altitude of a celestial body — such as the Sun — above the horizon, you use a ruler-like scale on the back of the astrolabe called the “alidade.” Holding the astrolabe vertically and aligning the alidade with the Sun, the degree markings along its edge tell you its height. With this information, you can rotate the disks and spider on the front face to calculate the time of day, the season, and even more. This is how a three-dimensional sky is modeled on a two-dimensional instrument.

More Than Just Stars: What Was the Astrolabe Used For? 🗺️

The astrolabe was a versatile tool used for many different purposes. For sailors, it was a guide in the middle of the ocean. By observing the North Star at night or the Sun during the day, they could determine their latitude — essentially functioning as the GPS of their time.

For Muslim scholars, the astrolabe was vital in daily life and religious practice. It was used to precisely determine prayer times based on the Sun’s position and to find the direction of the Kaaba (the qibla). Architects also used it to measure the height of buildings and conduct land surveys.

Who Used the Explorer’s Treasure, and Where?

The astrolabe was an indispensable tool for many brilliant minds and daring explorers throughout history. Here are some of those who used it and where they used it:

• Astronomers used it in observatories and scientific centers. Figures such as the renowned scholar al-Bīrūnī and Maryam al-Ijliyya, famed for her skill in astrolabe construction, relied on this instrument to unravel the secrets of the sky.
• Sailors and explorers used it aboard their ships in open seas. Explorers like Christopher Columbus, who discovered America, and Ottoman admiral Seydi Ali Reis, who sailed the Indian Ocean, found their bearings across vast oceans using the astrolabe.
• Muwaqqits served in cities, especially in timekeeping houses adjacent to mosques. For example, Mustafa ibn Ali al-Muwaqqit, who lived in the 16th century, was a leading expert who used the astrolabe to measure time with great precision and determine prayer times.
• Engineers and cartographers used it while working in the field and in cities. They employed the astrolabe’s angle-measuring capability to create maps and design building plans.

Journey Through Time ⏳

The fundamental principles of the astrolabe were first developed over 2,200 years ago during the Hellenistic period in ancient Greece. However, it was the scholars of the Islamic Golden Age who refined and transformed it into a far more practical instrument. For instance, Muhammad al-Fazari, who lived around 1,200 years ago, is credited as the first person in the Islamic world to construct an astrolabe. Later, great scholars such as al-Khwarizmi, al-Bīrūnī, and Zarqālī developed new types, including “universal astrolabes” that could be used at any latitude and even across the entire globe. For hundreds of years, this instrument remained indispensable to science and technology in both the East and the West.