About Jantar Mantar
Jantar Mantar is the largest of the five observatories built by Sawai Raja Jai Singh. Located in the city of Jaipur, Jantar Mantar draws its name from Sanskrit terms 'yantra' and 'mantra'. The former term means instrument while the latter means formulae. Built between the period of 1728-34, the Jantar Mantar is based on the astronomical studies conducted by Sawai Jai Singh and his men around the world. One of his men brought a manual which was a copy of La Hire's "Tables". Accordingly, Jai Singh ordered the construction of the observatories based on the information provided in this manual.
Jai Singh had to make choice regarding the material used for the construction of the observatory. He had the option of using either metal or masonry instruments and he preferred the latter to the former. Infact, he himself designed the stone and masonry instruments of the observatory.
Jantar Mantar is hugely attractive destination for scholars, however, common people are little aware about its importance. A visit to Jantar Mantar makes tourists realize that the Rajput rulers were not just ardent patriots and admirer of royalty but also highly intellectual and observant. As such, though the place is more related to science, yet it has a historical importance attached to it.
Instruments in Jantar Mantar
Kranti Yantra is meant to measure the latitude and longitude of the celestial body while the Diganta Yantra measures the azimuth (the arc of celestial great circle from Zenith to horizon) of the planetary bodies. The small and the large Ram Yantra also measure the azimuth along with altitude.
The Jai Prakash Yantra is used to find out the exact position of the celestial body during day and night. It is a two hemispherical marble bowl structure with 12 zodiac gnomes behind. Gnomes are shadow indicators or sun dials that can also be used to ascertain time. The Jai Prakash Yantra is also meant for monitoring the work of other instruments in the observatory. It is said that this instrument is the most important work of Jai Singh in the observatory. The central position of the instrument in the observatory also bolsters this point.
The big sundial or the Samrat Yantra is one of the major attraction of the observatory. The ramp that serves as an indicator is oriented towards north and points exactly at the Celestial North Pole. The shadow of the indicator falls on the eastern and the western scales that are shaped like a wing. These shadows indicate a pretty accurate timings. The ramp of the big sundial is not open for public as observers still use them. The little sundial, which is one tenth of the larger sundial in size, is however open for public.
Other instruments of the observatory includes the Rashivalayas Yantra, Dakshina Yantra, Disha Yantra, Unnathamsa Yantra, Raj Yantra, Narivalya Yantra and the Dhruv Yantra . There are quiet a few other instruments in the observatory as well.