Jantar Mantar, also known as Delhi Observatory, is a group of large red and white stone structures (or yantras) built in the 18th century to perform astronomical and astrological calculations. It was designed by Jai Singh II, ruler of Jaipur, and was the first of five such observatories across the country. It provided a surprisingly accurate way of calculating time, as well as solar and lunar movements. This was done by measuring the length and direction of shadows cast by the yantras.
The observatory is set in a garden with palm trees and flower beds. Today many visitors can be seen just enjoying a pleasant stroll around the grounds.
The Samrat Yantra is a 70 ft high triangle that points towards the North Pole. It acts as a sundial, casting shadows onto marked quadrants on either side. This yantra is considerably more sophisticated than other sundials in use in the 18th century, indicating hours, minutes and seconds, as well predicting the position of other celestial objects.
The design of the two circular Ram Yantras is said to be unique to the observatories of Jai Singh II. Each contains a central pillar surrounded by 30 wooden radials at regular intervals, making a full circle of 360 degrees. The yantras are open at the top, allowing shadows to be measured on the scales marked on the walls, floor and pillars. These measurements were used to calculate the altitude of stars and planets.
Jai Prakash Yantra
The two giant hemispheres set into the floor were intended as a reflection of the celestial hemispheres, and were used as a way of cross-checking the measurements obtained from the other instruments. When in use, a metal ring is suspended in the middle by means of crosswires, and adjusted to mark the position of the sun. The shadows are then measured against markings on the side which indicate the location of various constellations of the zodiac.
The Mishra Yantra is unique to the Delhi Observatory, and was designed by the son of Jai Singh II. It has five distinct parts which measure longitude, latitude, height and movement of various heavenly objects. This enables the calculation of local time in various cities of the world.
The Mishra Yantra is constructed in two halves, for the determination of time before and after noon.
Visiting Jantar Mantar
Jantar Mantar is close to Connaught Place, and the nearest Metro station is Rajiv Chowk.
It is open from sunrise to sunset and there is a small entrance charge. You may prefer to visit at the beginning or end of the day when the shadows are longer and the workings of the observatory can be seen to best effect.