Muslim Astronomers and Their Impact on Europe

Arabia, the birthplace of Islam, boasts a magnificent nocturnal sky adorned with a plethora of stars, resembling a treasure chest of cosmic gems. Throughout antiquity, these stars served as crucial navigational beacons, particularly within the expansive deserts. The celestial bodies not only guided travelers but also bestowed the night sky with a constellation of Arabic names—Aldebaran, Rigel, Fomalhaut, Betelgeuse, Deneb, Altair, and more. With the advent of Islam, astronomy gained revered significance, and these starry designations endured, maintaining their relevance in contemporary times. As Islam extended its influence across vast territories, the necessity of aiding travel within the empire was met by the enduring stars, offering unparalleled guidance across the expansive landscape.

Astrology also attracted caliphs with its power to predict, despite the objections of many theologians. The rise of the Abbasids, for instance, brought some of the ancient Persian Zoroastrian tradition of astrology right into the heart of Islam, and each Abbasid caliph had his own personal astrologer from the Naubakht dynasty and many historians say that the pursuit of astrology was a key reason for the development of observatories.

Demand and Faith

In our discussion, we're focusing on how astronomy is important in Islam and how much trust they have in stars. In Islam, there are three main teachings that relate to astronomy, and these teachings have a big impact on how people relied on the stars. These teachings show how faith and the stars are connected, and they also show how stars have shaped Islamic traditions and way of life.

  • Muslims were told to pray daily at five specific times- Sunset, late evening, dawn, soon after midday and late afternoon. The only way to be sure when to pray would be to observe the angle above the horizon of the sun or the stars in the sky. And if it was important to do it at precisely the correct time, then the more accurately that could be calculated, the better. It even led to the great invention of astrolabe, a device for computing angles developed in Greece.
  • Muslims are expected to pray towards the Ka’bah in Mecca as Qiblah. Astronomers are mathematicians who worked hard at getting the Qiblah right from every part of the world. In addition to that there were never any questions in the Islamic world at that time about the earth not being round. This is complex spherical geometry, and also demands very accurate observations of the reference points in the night sky – since even the tiniest error could throw the calculations out.
  • The Islamic calendar consists of twelve lunar months in a year. Each lunar month starts with the moon’s first visible crescent. Predicting exactly when that crescent will appear presented early Muslim astronomers with a real challenge.

Most mosques employed an official timekeeper as Muwaqqit to help the faithful pray on time. They were competent astronomers. Islamic rulers were also happy to fund observatories and astronomical instruments. They had a strong interest in these activities. Many of the observatories were raised in Islamic era thanks to these rulers.

Astronomical Observations

Muslim astronomers pursued their studies during various ruling periods, often conducting their work within observatories that were typically treated as private domains. For instance:

  1. The Scientist asan Ibn al-Hytham had worked in Fatimid Cairo during 11th century under ruler Al-Hakim
  2. Ibn al-Shātir was Muwaqqit and astronomer in Damascus’ largest mosque.
  3. Ibn Sīna worked under many rulers during 11th Century Central Asia.
  4. Nāsir al-Dīn al-Tūsī worked under Helagu Khan in the Maragha

The patronage of rulers played a pivotal role in fostering the growth of observatories, a significant contribution originating from Islam. Among the noteworthy examples are:

  • First observatory in Muslim world was in 9th Century Baghdad in the 820s by Al-Ma’mūn on Mount Qasioun near Damascus.
  • Observatory in 10th century Cairo under Fatimid Caliphate.
  • Another one in the 19th Century Maragha in which Nāsir al-Dīn al-Tūsī worked under Helagu Khan. It was famous for its data
  • Samarkand Observatory in the 19th century by Tamerlane’s grandson Ulug Beg. It was the largest of all.

These observatory wasn’t qualified for Byt al-Māl financing like for mosques, hospitals, schools etc. Regrettably, these observatories often ceased to exist after the passing of their initial patrons. In addition to these observatories, the Islamic world also witnessed the creation of numerous "Zij" tables, which were employed to comprehend the motions of celestial bodies, and "astrolabes," instruments designed to calculate the angles of stars. It's worth noting that these developments had their origins in Greece.

Ibrāhīm al-Fazarī, an early astronomer under Caliph Al-Mansūr (754-15 CE) made a translation for ‘Sindhind’ of Brahmagupta. It is thought that it is the reason for the coming of Indian numerals to Arabic, a task completed by Al-Khawārizmī. Under Caliph Hārūn Rashīd, Al-Fazerī made the first known astrolabe in Islamic world. It became a main navigational aid for centuries. Astrolabes can tell where the stars will appear from your current latitude. Few years after Al-Fazarī's astrolabe, in the reign of Caliph Al- Ma’mūn, many great works of Ptolemy translated to Arabic. It shaped the course of Islamic astronomy throughout the medieval period.

Using these observatories, Arabic astronomers gradually made more accurate measurements on earth and heavens. They even calculated the circumference of the earth as 24, 535 miles which is actually 24.906 miles (a small deviation). Nearly all Islamic Scholars like Ibn Sīna, Ibn Rushd, and Mūsa bin Maymūn contributed to Astronomy. The Zij tables of Al-Khawārizmī and Al-Battānī were picked up by Spanish astronomers like Maslama al-Majrītī in the 10th century which paved the path of astronomy to Europe.

Ptolemaic System

Claudius Ptolemy, a Greek polymath, living in Alexandria during 90-168 CE, left an indelible mark with his significant works. "Geography" stood out as a definitive world atlas for an impressive span of 1,300 years. Equally noteworthy is ‘Almagest’ which provides a complete model for the movement of sun, moon, planets and stars. According to him, every celestial body is moving in perfect circular motion and all are revolving around Earth. However, his model encountered a challenge: while stars obediently traced perfect circles, the sun held the center position. This aspect of his theory presented a conundrum that perplexed astronomers for centuries.

Over time, Islamic astronomers started entertaining the notion that there could be issues with the Ptolemaic model. The great polymath Ibn Al Hytam (Alhazen) wrote the book “Doubts about Ptolemy" (Al-Shukūk al-Batlamayūs). In this work he raised questions against the Ptolemaic system. In 12th century, Ibn Rushd declared that “The astronomers of our time offers no truth”

Next few centuries, Islamic astronomers began to make experiments on Ptolemy's model to make it right. A key breakthrough was made by the brilliant astronomer Nāsir al-Dīn al-Tūsī born in Tus, Khorasan in 1201. His childhood was when the forces of Mongol commander Genghis Khan’s began invasion in Asia. Fearing them, he was sent to Nishapur. When his home town was savaged by Mongols, he decided to work under the governor of Alamut in a mountain fortress. As Alamut is the center power of the Isma'ili branch of Islam, it led him to the Isma'ili faith.

For thirty years he devoted himself to astronomy and wrote a number of important books which only reached Europe much later. In 1256, Mongols under Helagu Khan, grandson of Genghis Khan, conquered Alamut. Al-Tūsī not only survived it, but was taken by Helagu Khan as his personal astrologer. Helagu Khan built the best equipped observatory in Maragha, Persia, and a library baring about 400,000 books. Thus Al-Tūsī got access to all astronomical theories and data.

His most important invention was Zij al-llkānī, named after the Ilkhanate Empire, the most complete and accurate set of tables. He also established trigonometry as a separate branch of math. His ‘Theory of Tusi Couple’ was a way of showing how realistically uniform motion in circles can actually end up making something move in a straight line. Using this concept, he simplified the Ptolemaic system getting rid of upper planet problems (Saturn, Jupiter, and Mars).

However, challenges still remained when it came to understanding Mercury and the moon. During the 14th century, Qutb al-Dīn al-Shīrāzī made strides in addressing the Mercury dilemma, amalgamating insights from his mentor Al-Tūsī and incorporating concepts from the 13th-century astronomer Mu’ayyad al-Dīn al-Urdī. Taking this a step further, Ibn Al-Shātir, serving as muwaqqit at the Great Mosque of Damascus, achieved a breakthrough by eliminating all superfluous motions except for epicycles, even including those related to the moon. In essence, by the late 14th century, Islamic astronomers had organized a comprehensive transformation of the Ptolemaic system.


It was the 16th century when Copernicus showed the world that the earth is moving around the sun along with other planets. But this concept failed to give accurate astronomical predictions until Kepler showed that the paths of planets are not perfectly circular, but slightly elliptical. Then the question ‘how do the celestial bodies hold together’ was only answered by Newton's theory of gravity. In conventional accounts, the narrative seems to leap straight from Ptolemy to Copernicus. In these narratives, the ultimate Islamic contributions have disappeared and are misguided to be nothing.

But as a matter of fact, Copernicus acknowledged some of the data which he used to prove his theory from the charts of Al-Battānī and Al-Bitrūjī who were Muslim astronomers. In 1957, historian Otto Neugebauer noticed similarities between illustrations in Copernicus’ first masterpiece Commentariolus (1514) and illustrations in Ibn al-Shātir’s book in which he explained the motion of the moon. He also found another apparent illustration similar to Al-Tūsī’s Tadhkira (1260) in which he explained the ‘Theory of Tusi Couple’. It even has an apparent mistake in copying Arabic letters from Al-Tūsī’s illustration. Many scholars believe that Copernicus drew it directly from the work of Islamic astronomers. We can admit that Copernicus’ idea of the Heliocentric (sun-centered) universe was a seismic shift in astronomy. But it was a revolutionary result that paved its path through gradual chipping away in the Ptolemaic system over centuries by countless Muslim astronomers and their ingenious ideas. These contributions are not to disappear in front of the world.  


Masood, E. (2009). Science & Islam: A History. Icon Books.

Al-Khalili, J. (2012). The House of Wisdom: How Arabic Science Saved Ancient Knowledge and Gave Us the Renaissance. Penguin Books; Reprint edition.

Morgan, M. H. (2008). Lost History: The Enduring Legacy of Muslim Scientists, Thinkers, and Artists. National Geographic; Reprint edition.

Saliba, G. (2011). Islamic Science and the Making of the European Renaissance. The MIT Press.

About the author

Muhammad Rishad from Kodur of Malappuram district,  is a degree student in the Department of Civilizational Studies at Darul Huda Islamic University, Kerala, India. He also pursues a Bachelor's Degree in history from Calicut University.


The views expressed in this article are the author’s own and do not necessarily mirror Islamonweb’s editorial stance.

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