****Jantar Mantar****

The Jantar Mantar is located in the modern city of New Delhi. It consists of 13 architectural astronomy instruments. The site is one of five built by Maharaja jai singh II of jaipur, from 1723 onwards, as he was given by Mughul emperor Muhammd Shah the task of revising the calendar and astronomical tables. There is a plaque fixed on one of the structures in the Jantar Mantar observatory in New Delhi that was placed there in 1910 mistakenly dating the construction of the complex to the year 1710. Later research, though, suggests 1724 as the actual year of construction.

The primary purpose of the observatory was to compile astronomical tables, and to predict the times and movements of the sun, moon and planets. Some of these purposes nowadays would be classified as astronomy.

Completed in 1724, the Delhi Jantar Mantar had decayed considerably by 1867.

The Samrat Yantra, is the huge sundial meant to measure accurate time of the day within half a second. A striking yellow structure on the right side stands 70 feet high, 114 feet long and 10 feet thick. 

The 27m high arm adjusted at an angle of 27 degrees reflects the local time accurate in four minutes and also measures the declination of the sun. Jai Prakash is an instrument designed by Sawai Jai Singh himself. The imagination consists of hollowed out hemispheres with markings on their concave surfaces which together ascertain the position of the sun and other heavenly bodies. Mishra Yantra is the only observatory that was not invented by Sawai Jai Singh II. The two pillars on the southwest of Mishra Yantra determine the longest and the shortest days in the year. 

Fascinatingly, one pillar overshadows the other in December while in June; it does not cast any shadow at all. Ram Yantra consists of two large buildings open to the sky. This yantra is used for measuring the altitude of stars. All these instruments are used for various astronomical calculations. 

Jantar Mantar of Delhi till date is used by modern day scholars to ascertain the determine position of astral bodies in our universe.

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