Muslim Contribution to the Field of Astronomy: Nasir Al Din Tusi and the Maragha Observatory

Nasir Al-Din Tusi helped initiate a complete change in the way we understand the universe today.

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Nasir Al-Din Tusi helped initiate a complete change in the way we understand the universe today.

Astronomy, the natural science dealing with celestial objects, has been an interesting matter of discussion since the birth of human beings – thus it has been thriving along with the development of humankind. Now we are at the zenith with stupendous knowledge of astronomy and the contribution of Muslim astronomers are mind-blowing throughout its history.

Muhammed ibn Muhammed ibn Hasan al Tusi is one among the countable Muslim astronomers with a miraculous contribution to the field of astronomy. He opened a new window to the world of astronomy which resulted in magnificent universal awareness and knowledge in astronomy. Also, he brought numerous sources of astronomy from different languages under a roof and conducted fascinating observations.

Maragha Observatory in northern Iran was established by his directorship and patronage of Ilkanid Hulagu in 1259, and it is mentioned as the first full-scale observatory including a library and school. It produced great astronomers and witnessed sound observations through his leadership. It was considered as the most advanced scientific institution in the Eurasian world of that period.

His work ‘The Astronomic Tables of Ilhans’ in four volumes is a combination of different studies conducted in the Maragha Observatory. Many treatises on practical astronomy, instruments, astrology, and cosmography had a great influence on dexterous astronomers. The work ‘Al Tadkira FI Ilmi Al haya’ is one of the most famous works of all time. The calligraphy inscription on his grave reads as ‘The helper of religion and people, the shah of the country of science. Such a son has never been born’.


In this article, my focus is on the astronomical contribution of the Muslim astronomer Nasir al din Tusi and his well-known Maragha Observatory. It is very interesting to realize the amazing contribution given by Muslim astronomers. On contrary to this, it is sad to know many Islamic contributions are always behind the curtain.

The personality Nasir al Din Tusi was not only an astronomer but also a theologian, scientist, physician, Persian polymath, mathematician, and architect to name a few. So his contribution could never be limited in this particular field of astronomy. He has played a vital role in developing Islamic Golden Age as well. Tusi Couple is one among the great contribution of Nasi Al Din Tusi, which was later developed by Ibn Shatir and resulted in the astonishing discovery of the Heliocentric Galaxy.

Tusi also had written about Milky Way in his book ‘Tadkira’, stating: “The Milky Way, the galaxy, is made up of a very large number of small and tightly clustered stars, which on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color”. But the world came to this reality by the finding of Galileo in 1610 through a telescope, where Galileo talks about the cluster of faint stars. Similarly, in his contribution to mathematics by finding spherical trigonometry he lifted the level of mathematics into another stage. Other than this, he had also written many works in biology, chemistry, and logic in which he had challenged and rectified the big scholars of the Greeks.

Tusi Couple is another marvellous contribution by Tusi for the world of astronomy. Later, many mathematicians and engineers would use this Tusi Couple for developing their theories in their field other than astronomy. Hypocycloid is one among them used as straight line mechanisms. Gerolamo Cardano designed a system known as Cardens Movement for his mathematical thrive.

The Observatory initiated by Tusi as the Maragha Observatory created a platform for many astronomers, even from China. More than just an observatory, it holds a great library, school, and center for scholars of different branches too. 

Nasir al din Tusi

Khwaja Mohammed ibn Mohammad ibn al-Hasan al-Tusi, or Nasir al-Din al-Tusi, was born on February 18, 1201, in Tus, medieval Kharasan (now north-eastern Iran), into a wealthy and learned Twelver Shi’ah family and died in 26 June 1274. Despite of living in a wealthy family, he was an orphan by losing father in his childhood. But he was extremely passionate by the words of his father to be a well-known scholar with mountainous knowledge in different branches of education as his father wishes. So it is very easy for us to find hard work, optimistic endeavors, and great interest in acquiring knowledge in all walks of his life.

His life objective initiated with acquiring knowledge of physics, logic, and metaphysics from his uncle and mathematics from different teachers. After a limited period of learning he shifted to Nishapur, which was a countable learning center of that period. It is amazing to know that he used to gain highly advanced topics in mathematics, philosophy, and medicine despite being only a teenager.

Later after completing his advanced studies, he moved for lecturing on his special field mathematics and astronomy. Then after completing his studies in early 1230 he took refuge from the Mongols, who had invaded Tus, at the Isma’ili fort, where he spent his time researching philosophy, astronomy, logic, and mathematics. In 1247, while he was at the Isma’ili capital in Alamut in 1256, the Mongols, an army led by Hulagu, invaded and captured him. However, he was later appointed as Hulagu’s scientific advisor due to his excellence in different branches of knowledge, talent, and abilities.

In the mid 13th century he began the construction of Rasad Khaneh Observatory in Maragha which was later named as Maragha Observatory, after seeking Hulagu’s consent and serving as its director till his death. It was equipped with sophisticated instruments and included a library and school. 

Works of Nasir Al Din Tusi

The works of Nasir Al Din Tusi are noteworthy. He had written ‘Ahrir al-Majisti’ (Commentary on the Almagest) as an introduction to trigonometry and showed various methods to calculate sine tables. In the span of studying at Mosul, he had completed a small booklet of philosophical Sufi compositions like ‘Awsaf al-Ashraf’ (The Attributes of the Illustrious) as well.

His four-volume ‘Zij-i ilkhani’ (Ilkhanic Tables), completed in 1272, is one of his major astronomical works, which indicates the research made at the observatory in his term of directorship. Among over 150 works he produced during his lifetime, he also translated the works of some eminent astrologers and mathematicians into Arabic – some being Archimedes, Autolycus, Ptolemy, Hypsicles, Theodosius, and Menelaus. Some of the most remarkable works are listed below.

  • Kitab shakl al qatta
  • Sharhe al isharath
  • Awsaf al ashraf
  • Thalkheesul mukhassal
  • Rawdayi taslim
  • Tajrid al aqaid
  • Akhlaqe nasri
  • Zij ilkhani
  • Alrisala alastrolobia
  • Altadkira fi ilmil haya

Tusi Couple

Generally, the Tusi Couple which was found (1247) by Nasi Al Din Tusi in his Tahrir Al Majesty was later used by many astronomers for miraculous researches. The Tusi Couple is a mathematical instrument in which one small circle rotates inside another larger circle that has twice the diameter of the small circle. The rotation of circles causes a point on the circumference of the smaller circle to oscillate back and forth in linear motion along the diameter of the larger circle.

The Tusi Couple is a modern usage for the instrument of Nasir al din Tusi, and the name was coined by Edvard Stewart Kennady in 1966. It is one among the hundreds of instruments from the Golden Islamic period; the reality is that it has a striking similarity with the De revelotionibus of Copernicus. So there are some mediums that worked to transmit the astronomical innovations from the period of Tusi to the late period of Copernicus. Now the scholars are at a point that there is a great chance for the transformation of ideas from Tusi to Copernicus through the translation of Arabic works of Tusi into Byzantine Greek and the spreading of ideas from Greek to Copernicus.

Tusi himself describes the Tusi Couple as: “If two coplanar circles, the diameter of one of which is equal to half the diameter of the other, are taken to be internally tangent at a point, and if a point is taken on the smaller circle — and let it be at the point of tangency — and if the two circles move with simple motions in opposite direction in such a way that the motion of the smaller [circle] is twice that of the larger so the smaller completes two rotations for each rotation of the larger, then that point will be seen to move on the diameter of the larger circle that initially passes through the point of tangency, oscillating between the endpoints.”

Later many mathematicians and engineers used this Tusi Couple for developing their theories in their field other than astronomy. Hypocycloid is one among them used as straight-line mechanisms. Gerolamo Cardano designed a system known as Cardens Movement for his mathematical thrive.

Tusi’s Legacy Today

Some of the modern era’s nods of recognition to Tusi include when a 60 km diameter lunar crater in the southern hemisphere of the moon was named after him as Nasiruddeen.

In another case, a minor planet ‘10269 Tusi’ discovered by Soviet astronomer Nikolai Stefanovich Chernykh in 1979 was also named after Tusi. And finally, the KN University of Technology in Iran and the Observatory of Shamakhy are both named after him.

Maragha Observatory

Maragheh is a known city in Northern Iran on the bank of the river Safi Chay. It is located in East Azarbaijan Province, 130 km from Tabriz, and has a population of 300,000. Maragheh is an ancient city situated in a narrow valley running nearly north and south at the eastern extremity of a well-cultivated plain opening towards Lake Urmia, which lies 30 km to the west.

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The town is encompassed by a high wall ruined in many places and has four gates. Two stone bridges in good condition are said to have been constructed during the reign of Hulaku Khan (1217- 1265), the grandchild of Ghengis Khan, who made Maragheh the capital of the Ilkhanate Empire.

Maragha Observatory is an ancient observatory, which was established in 1259 by Nasir al-Din al-Tusi. Located in the heights west of Maragheh, it was once considered one of the most prestigious observatories in the world. This observatory was built 167 years before the construction of the Samarkand Observatory. In its heyday, the observatory was quite reputable.

For instance, Chinese experts were dispatched to Maragheh by Emperor Kublai Khan to prepare a prototype. After returning to China, these experts built an observatory based on the Maragheh building. Later, models based on Maragha Observatory were built in Samarkand (Uzbekistan), Istanbul (Turkey), and Jaipur (India). Considerable parts of the groundwork are preserved in the ruins. In a 340 to 135 m² citadel-like area stood a four-story circular stone building of 28 m diameter. The mural quadrant to observe the positions of the stars and planets was aligned with the meridian. This meridian served as the prime meridian for the tables in the Zij-i Ilkhani, as we nowadays apply the meridian which passes the Royal Greenwich Observatory.

The Maragha Observatory was also the largest observatory in its time, consisting of a series of buildings occupying an area of 150 metres in width and 350 metres in length. One of these buildings was a dome that allowed the sun’s rays to pass through. There was also a library consisting of 400,000 volumes, which were plundered by the Mongol Empire during its invasions across Persia, Syria, and Mesopotamia.

Astronomers from across Persia, Syria, Anatolia, and even China were gathered at the observatory, and the names of at least twenty of them who worked at the observatory are known. The special thing about the observatory is the 20 meter to 44 meter deep wells and caves around it where astrologist Khajeh Nassir and his students could track down the movements and the location of stars in the sky. Maragha Observatory was not just a place for observing stars, but also a scientific organization that shouldered the task of training students in most scientific branches.

It is believed that several Chinese astronomers worked at the observatory and that they introduced several Chinese methods of computation. The Maragha Observatory was also reported to have had over a hundred students studying under al-Tusi at the observatory and was also the first observatory to benefit from the revenues of waqf trust funds. After al-Tusi’s death, his son was appointed the director of the institution, but it was later abandoned by the middle of the 14th century. A visit to the ruins of the observatory later inspired Ulugh Beg to construct his own large observatory at Samarkand to continue the astronomical research of the Maragha school from where it left off.

Hulegu Khan believed that many of his military successes were due to the advice of astronomers (who were also astrologers), especially of Nasīr al-Dīn al-Tūsī. Therefore when Tusi complained that his astronomical tables were outdated, Hulagu gave permission to build a new observatory in a place of Tusi’s choice. The library of the observatory contained 40,000 books on many subjects, related to astrology/astronomy as well as other topics. Bar-Hebraeus late in his life took residence close to the observatory in order to use the library for his studies. He has left a detailed description of the observatory, which helped preserve the memory of this incredible centre.

The Decline of Maragha Observatory

After 12 years of intense work by Khaje Nassir od-Din Tussi and the other prominent scientists, the observations and planetary models were compiled in the Zij-i Ilkhani, which later influenced Copernicus. The tables were published during the reign of Abaqa Khan, Hulagu’s son, and named after the patron of the observatory. They were popular until the 15th century.

It is not known with certainty until when it had been active. It turned into ruins as a result of frequent earthquakes and a lack of funding by the state. Shah Abbas the Great arranged for repair, however, this was not commenced due to the king’s early death. To save the installation from further destruction, Iran’s Cultural Heritage and Tourism Organization (ICHTO) built a dome-framed shelter and it plans to hold an exhibit of astronomical devices used at the Maragha Observatory.

Iran will commemorate the 750th anniversary of the Maragha Observatory, which is one of the oldest and biggest observatories established before the invention of the telescope.

Astronomers of Maragha Observatory

A number of other prominent astronomers worked with Tusi there, such as Muhyi al-Din al-Maghribi, Mu’ayyid al-Din al-‘Urdi, from Damascus, Qutb al-Din al-Shirazi, and Hulagu’s Chinese astronomer Fao Munji whose Chinese astronomical experience brought improvements to the Ptolemaic system used by Tusi.

Muhyi al din al Maghribi

He is one of the great astronomers who worked with Nasir al din Tusi in the Maragha Observatory. One of his famous contributions to astronomy is the book ‘Khulasat al Majesti’ which is the summary translation of Almagest.

Further, he had played a vital role in creating Astrolabe, which determined the meridian line and revolution of a sphere. ‘Tastih al Astrolabe’, ‘Risalat al Khata wal igur’, ‘and Al Musahhah bi adwar al anwar ma al rasad’ are some of his notable works.

Mu ayyid al Din al Urdi

He is remembered as the instrument maker in the Maragha Observatory. He was called by Tusi to his Observatory by realising his dexterous skill in designing and constructing instruments. He had played a major role in building the observatory by creating water machines to bring water to the hilltop where the observatory works with large water wheels.

Al Urdi had also written great works such as ‘Urdi risala fi kifayatil arsad’, which is preserved in Paris. Mural Quadrant, an armillary sphere, a solstitial armilla, and equinoctial armilla are made by him for measuring the ecliptic longitude and latitude, determining the obliquity of the ecliptic, and determining when the sun entered to the equatorial plane as the path of the sun.

Qutub Al Din Al Shirazi

The background of his family is spiritually exalted. In October 1236 he was born in Kazerun. His lovely father Zia al Din Masud Kazruni was a physician by profession along with staunch spiritual touch. The life of Qutub al din al Shirazi has many similarities with Nasir al-din Tusi in great interest in the field of astronomy. Additionally, Qutub lost his father at the age of 14 and his medicinal studies with his father were later continued by his uncle and many other great scholars.

Later he became highly attracted to the Maragha Observatory of Tusi and spend a short span of time in the observatory. He used to study from Tusi many works, especially of Avicenna. Later Tusi also taught him astronomy and after realizing his dexterous ability in astronomy, Tusi asked his son Aṣil-al-Din to work with him and complete the book Zij. ‘Ektiarat e mozaffari’, ‘Nehayat al edrak’, and ‘Altuhfa al sahiya fi haya’ are some of his major works on astronomy.


The Maragha Observatory had given birth to many fascinating astronomical instruments and works which lead to reaching the zenith of the astronomical stand. Great astronomer Nasir al-Din Tusi has a miraculous contribution to astronomy. Along with that, a number of other prominent astronomers worked with Tusi in the observatory, such as Muhyi al-Din al-Maghribi, Mu’ayyid al-Din al-‘Urdi, from Damascus, Qutb al-Din al-Shirazi, and Hulagu’s Chinese astronomer Fao Munji whose Chinese astronomical experience brought improvements to the Ptolemaic system used by Tusi.

I hope this article helps shed light on the astronomical contribution of Muslim astronomers in the Islamic Golden Age and helps remind us to remember the key role played by Muslim scientists to lift our previous astronomical level from oblivion and filled with assumptions to modern realistic astronomy.

I hereby express my heartfelt gratitude to Markhins Khykha Bangalore and Markaz Sharia City Calicut for giving me a great opportunity to present the paper. 


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