.....Amber. He was a prominent statesman, lawmaker, and reformer. Jai Singh was born in 1688. In the present-day state of Rajasthan, in the Amber area. When his father, Bishan Singh, passed away; he was 12 years old, he ascended the kingdom. The young king was intelligent, eager to learn, savy in politics and society. He created the city of Jaipur, which bears his name, and was in charge of most of its design, among his many other subsequent accomplishments.

Many events influenced Jai Singh to think more about astronomy. He thought that the nation needed to be educated on the subject of astronomy. Jai Singh first met Pandit Jagannatha Samrat, who would eventually become his guru and principal astronomical counsellor, during the Deccan campaign, which took place about 1700. After the campaign, Jagannatha travelled with Jai Singh back to Amber, where he studied Jai Singh's enormous library of different scriptures to further his education. The design of the Jantar Mantar was greatly influenced by Jagannatha, who served as Jai Singh's principal astronomer, and the two men were lifelong friends. His interest may have been kindled as early as 1702 by Jagannatha Samrat. Despite local wars, foreign invasions, and consequent turmoil, Jai Singh found time and energy to build astronomical observatories.

When Jai Singh dreamed of his enormous observatory project in the early 1700s, the telescope had been in use by European astronomers for almost a century.

Bharatiya astronomers had improved the instrument by the 14th century, making unique versions with great craftsmanship and attractive adornment. Jai Singh would have acquired his early astronomical training through the use of the astrolabe, and one of the early instruments at his observatory in Jaipur is the Yantraraja, a large 8-foot-tall astrolabe. Despite the importance of the astrolabe in astronomical computations, Jai Singh observed that previous tables were frequently out of sync with current observations. His own study revealed that the brass instruments used to generate the previous tables had lost accuracy owing to wear on their mechanical components. He decided to base his observatories on naked eye observation. Natural occurrences, such as the apparent movement of stars and planets, became part of the Hindu worldview and influenced a wide range of daily activities, from agricultural practices to religious ceremonies to personal decisions about when and who to marry.

Five observatories were built at Delhi, Mathura in his Agra province, Benares, Ujjain capital of his Malwa province, and his own capital of Jaipur. His astronomical observations were remarkably accurate. He drew up a set of tables, entitled Zij-i-Muhammadshahi, to enable people to make astronomical observations. He had Euclid's "Elements of Geometry" translated into Sanskrit as also several works on trigonometry, and Napier's work on the construction and use of logarithms. Relying primarily on Indian astronomy, these buildings were used to accurately predict eclipses and other astronomical events. The observational techniques and instruments used in his observatories were also superior to those used by the European Jesuit astronomers he invited to his observatories. Termed as the Jantar Mantar they consisted of the Ram Yantra (a cylindrical building with an open top and a pillar in its center), the Jai Prakash (a concave hemisphere), the Samrat Yantra (a huge equinoctial dial), the Digamsha Yantra (a pillar surrounded by two circular walls), and the Narivalaya Yantra (a cylindrical dial).The Samrat Yantra is a huge sundial. It can be used to estimate the local time, to locate the Pole Star, and to measure the declination of celestial objects. The Rama Yantra can be used to measure the altitude and azimuth of celestial objects. The Shanku Yantra can be used to measure the latitude of the place.

Sawai Jai Singh's Jantar Mantar, which is primarily located in New Delhi, is made up of 13 different architectural devices with astronomical vistas. The primary purpose of building this observatory was to assemble a number of astronomical tables that are necessary for forecasting time as well as the movements of other celestial bodies, such as the location of the sun and moon and the motion of other planets. Jantar Mantar contained 20 different fixed apparatus for astronomical observation. The main concept behind the Jantar Mantar's construction was "Ptolemaic positional astronomy."

In 1728, he also established his new, brilliantly planned city Jaipur, 200 km southwest of Delhi, by merging features of the ancient Hindu book on architecture, the Shilpa Shastra, and designs of several European towns of the time with Jai Singh's own ideas.Jaipur was built on a strict timetable and with only sensible, scientific principles. Right angles cut across the city's vast streets. Jaipur boasted 119 feet wide main streets that were perpendicularly intersected by 60 feet wide auxiliary streets, which were further honeycombed by 30 feet wide lanes and 15 feet wide by-lanes. The streets were lined with beautiful, harmonised houses and shade trees, and the city was well-equipped with water conduits and wells. European travellers of the time, such as the Frenchman Louis Rousselet and the English Bishop Heber, were blown away by Jai Singh's unsurpassed skill in city building.

Jai Singh's great love though was astronomy. He was a scholar with an eclectic collection of astronomical manuscripts and tables from Arabia and Europe, including the Englishman John Flamsteed's 'Historia Coelestis Britannica,' the Portuguese Pere de la Hire's 'Tabulae Astronomicae,' the Turkish royal astronomer Ulugh Beg's tables 'Zij Ulugh Begi,' and the Greek Ptolemy's 'Almagest. According to modern historians other considerations also may have influenced Jai Singh and his astronomy. In the political turmoil of his period, erecting these colossal monuments may have fit both his desire to retain good standing with the seat of power in Delhi and his need to maintain control in his own province. Jai Singh's work is better understood as part of the global research into astronomy that took place in the eighteenth century.

Although he studied Hindu astronomy manuscripts, his knowledge of the Zj-i Ulugh Beg and proficiency with Graeco-Arabic equipment show that he went beyond a traditional Rajput education to explore a larger scientific literature.

References:

1. Bhatnagar VS (1974) Life and times of Sawai Jai Singh, 1688–1743. Impex India, Delhi

2. Sharma VN (1995) Sawai Jai Singh and his astronomy. Motilal Banarsidass, Delhi

3. Garrett A, Guleri C (1902) The Jaipur observatory and its builder. Pioneer Press, Allahabad

4. Sarkar, Jadunath; Simha, Raghubīra (1994) [1984]. A history of Jaipur: c. 1503-1938. Hyderabad: Orient Longman.

5. https://en.m.wikipedia.org/wiki/Jai_Singh_I

6. https://ui.adsabs.harvard.edu/abs/2015hae..book.2017J/abstract

7. https://www.researchgate.net/publication/279384327_Observatories_of_Sawai_Jai_Singh_II