Jantar Mantar Observatory Print
Written by Yogesh Soman   
Saturday, 25 March 2006 23:46


In early eighteenth century, a supernova, known by the name Sawai [[Jai Singh II]], exploded on the horizon of Indian Astronomy. During the brief period of his life, he tried to arouse Indian Astronomy which had been in a deep slumber for almost five centuries. He tried to give it a new life by bringing in new ideas from west. A chain of magnificent observatories known today as 'Jantar Mantar' (also known as [[Yantra Mandir]]) arose due to his efforts.

Here we are going to learn a little about these observatories and what sort of observations can be carried out from them. But before we take a tour of the Jantar Mantar itself, let us try to know a little about Sawai Jai Singh and the politico-historical situation prevalent in the early years of the eighteenth century.

Sawai Jai Singh and his times

Sawai Jai Singh, the statesman astronomer of India, was born to a royal family on November 3, 1688 in the town of Amber in the state of Rajasthan, India. One of Jai Singh's ancestors, Bharamala or Biharimala (d. 1573), recognised the ascendency of Mughal power and accepted the suzerainty of the emperor Akber in 1562. This made the house of Amber the most influential of all the Rajput houses serving the Mughals. Bharamala's descendents, Mana Singh (1543-1614) and Mirza Raja Jai Singh (1611-1667, great grand father of Sawai Jai Singh), were highly regarded nobles at the Mughal court and were entrusted with important missions.

Jai Singh displayed interest in mathematics at an early age. He had two manuscripts on astronomy copied for him when he was only thirteen. However, his formal education was cut short at the age of eleven when his father died, and he had to take charge of the administration. He ascended the throne of Amber on January 25, 1700. However, he continued his studies along with the discharge of his princely duties and soon acquired mastery over the subjects of astronomy and mathematics.

During the next ten of fifteen years of troubled and uncertain times in the history of India and Delhi, Jai Singh by clever politics became the largest single land owner amongst the kings of Rajasthan. It is said that at the peak of his time, he owned all the land between Delhi and the shores of Gujarat at Surat.

With great wealth and resources available to him as a powerful ruler, Jai Singh embarked upon an ambitious program of reviving astronomy in India. To this effect, he designed instruments, built observatories, compiled an excellent library, assembled competent astronomers of different scientific backgrounds, and sent a fact-finding scientific mission to Europe. His scientific career lasted more than 20 years until his death in 1743 at age 54.

Decision to build Observatories

Sawai Jai Singh had noted that the astronomical calculations based on the existing planetary tables did not always agree with observations. The problem was especially serious with the appearance of the new moon - the computations of which did not agree with the observations.

Discrepancies were also to be found in the time of rising and setting of the planets, and the seasons of eclipses of the sun and moon. These times were important both from purely astronomical point of view as well as with the important decisions relating to governance and other religious activities. In order to remove these errors new sets of observations were necessary. Thus with the view of setting the astronomical tables straight, Sawai Jai Singh approached the then mughal emperor Muhammad Shah with the request for permission to build the observatories.

He built five observatories in total, which are known today as 'Jantar Mantar'. They were at Jaipur, Delhi, Mathura, Ujjain and Varanasi and were completed between 1724 and 1735. The one at Jaipur was the largest with the maximum number of instruments. The observatory at Mathura vanished sometime around 1850. Those at Varanasi and Ujjain exist in various degrees of preservation.

The idea behind building a number of observatories at different locations in the northern India was to make the same observations from different places and thus reduce the errors introduced due to the limits of human vision.

While building the observatories Jai Singh had the choice of constructing either metal instruments or masonry instruments. The metal instruments, constructed according to the texts of the Islamic school of astronomy, did not measure up to Jai Singh's expectations. He discarded them in favour of the instruments of stone and masonry that he himself designed. He tried to achieve the desired precision through their large size, and steadiness from the relative inflexibility of their structures. A French Jesuit, du Bois, writes that Jai Singh prepared wax models of these instruments with his own hands.

Before constructing their masonry instruments, Jai Singh and his associates selected a suitable ground first and leveled it with water standing in masonry channels built just for this purpose. Such masonry channels may still be seen at Jaipur and Ujjain. Next, north-south and east-west directions were marked on the ground, the procedure for which had been known for a long time and described in standard texts such as the Suryasiddhanta.

Just as in any other observatory of medieval times, Jai Singh's observatories primarily housed time-measuring and angle measuring devices. Jai Singh graduated his time measuring devices according to the dexagesimal scheme in which a 24-hour day is divided into 60 parts of ghatikas, and the ghatikas are in turn divided into 60 subparts known as palas. For measuing angles, he divided a circle into four quadrants of 15 main divisions each. He partitioned the main divisions further into six subdivisions of one amsa or one degree each. He divided the degree-divisions, as the scale permitted, into minutes or kalas. Sixty kalas equaled one amsa or degree. Any deviation from this division-scheme seen presently at his observatories is purely a modern adaptation. It has nothing to do with Jai Singh. The scale markings on Jai Singh's time-measuring instruments had zeros on the meridian line, and 15-ghatika marks along the east-west line. These instruments thus measured time from midday or midnight. The angle-measuring instruments had their zeros on the east-west line.

Masonary Instruments

Listed below are the masonary instruments built by Sawai Jai Singh.

  1. Samrat Yantra
  2. Sasthamsa
  3. Daksinottara Bhitti Yantra
  4. Jaya Prakasa and Kapala A
  5. Nadivalaya
  6. Digamsa yantra
  7. Rama yantra
  8. Rasivalayas

Jai Singh's Astronomers

For his ambitious program in astronomy, Jai Singh assembled a large group of scholars with backgrounds in different traditions of astronomy. At his observatories, Hindu pundits, Muslim munajjimun (astronomers), and European Jesuits worked side by side. The Hindu pundits, his teachers, later became the mainstay of his programme, translating and copying astronomical texts, erecting observatories, and carrying out the day-to-day operations of his observatories.

The astronomical activities of Jai Singh's Hindu astronomers may be divided into four categories

  1. Erecting instruments and taking data at the observatories,
  2. Writing texts and commentaries,
  3. Translating from other languages, and
  4. Collecting or copying books for the royal library.

The Hindu pundits helped Jai Singh erect stone and masonry instruments. Their efforts in this regard are praiseworthy. The Great Samrats and other yantras of Delhi and Jaipur had a very high degree of accuracy.

They also wrote a large number of books and commentaries. However, these texts and commentaries were based mostly on the works of their predecessors. There was little original material in their works. It appears that the pundits did not wish to break away from a tradition which for all practical purposes had become stagnant. They translated a great number of texts. The credit, however, in part at least, should go to Jai Singh. He realised more than any one else that the astronomy of the country needed an infusion of fresh ideas, and that there was much to be learned from other traditions, such as from the Islamic and the European. Having reached this conclusion, he made arrangements for translating astronomical and mathematical works into Sanskrit. However, these translations turned out to be of those works which, in retrospect, had become outdated in the astronomical circles of Europe.

Delegation to Europe

Had Jai Singh remained content on this, his name would have had an assured place in the Indian history. He didn't and that is what separates a good astronomer/scientist from a visionary. Jai Singh was far ahead of his times and had realised the importance of the new ideas imerging out of the work being done in Europe. He also realised that exchange of ideas are a vital point in the development of any science and so sent a scientific fact finding mission to Europe.

The delegation, the first of its kind from the East, left Amber in 1727. The Raja saw to it that the delegation was taken good care of on its way to the seaport and wrote letters to this effect to his friends. The delegation travelled to Goa, paid a courtesy visit to the Portuguese viceroy, delivered presents to him, and then finally reached Portugal in January, 1729. It was led by Father Figureredo, the rector of the college of Agra, and it had two additional members.

The delegation stayed on in Portugal for a few months and finally returned to India with instruments, books, and astronomical tables, including the tables of de La Hire published in 1702. The delegation landed at Goa in October or November, 1730 and finally reached Jaipur in July 1731.

The delegation brought back with it European tables and instruments, but it did not bring back any information regarding the theoretical advances of astronomy in Europe. For example, it did not bring any books of Newton, Galileo, Kepler, or Copernicus. The reason is quite obvious. The relentless war waged by the Church in the aftermath of Galileo's trial had taken its toll in Catholic Europe. By the time Jai Singh's mission under Fr. Figueredo arrived in Europe, there was not a single scholar left in the Iberian Peninsula, particularly in Portugal, who could speak about Kepler or Newton. In Portugal, where King John V reigned, the Holy Office of Inquisition had cleansed the institutions of higher learning of all Copernicans decades before.

Because the mission under Fr. Figueredo never stepped outside the Catholic world, so far as neo-astronomy was concerned, it produced very little of substance. Unfortunately, the Raja seemed to have had no alternative but to rely on the Jesuits to lead his fact-finding mission to Europe because no high-born Hindu in those days would dare 'to cross the ocean' and thereby risk 'losing his caste'.

In retrospect, it appears that the Raja relied too much upon and was clearly influenced by his Jesuit assistants who erected an invisible shield between him and the so-called heretical neo-astronomy they avoided. To the end of his days, Jai Singh trusted the expertise of these faithful servants of the Church and made no attempts to consult anyone else from a country such as England or Holland, where the Copernican revolution had gained a solid footing. European involvement with the astronomical program of Jai Singh produced mixed results. On one hand, Europeans introduced Indian astronomers to improved methods of calculating astronomical problems, particularly in the use of logarithm. On the other hand, these Europeans held back from Indian astronomers the theoretical advances made by Copernicus, Gallileo, Kepler and Newton.


Despite his best efforts, Jai Singh remained to the very end of his days a medieval astronomer, the last link in the tradition of Nasir al-Din al-Tusi and Ulugh Beg. It is an unfortunate fact that the science of astronomy, despite Jai Singh's multifaceted efforts, did not revive in India. Jai Singh failed to usher in the modern age of this science in his country. The neo-astronomy came from an entirely different route, i.e. , the colonial British rule in the North.

Jai Singh approached his astronomical researches with an open mind. Before embarking upon his project, he studied what was available to him. Moreover, during his investigations, he kept this attitude alive. His search for better instruments continued even after his observatories had been built. According to du Bois he was ready to put aside his own tables if better ones were available. Jai Singh's accomplishments were medieval in retrospect, but his outlook was quite modern. His efforts were truly secular. For him scientific knowledge had no religion or nationality. Astronomers of all faiths participated in them. This fact alone is a great compliment to a ruler born in an environment and age of intolerance and bigotry


Last Updated on Thursday, 30 March 2006 23:46