Jantar Mantar, built between 1728 and 1734 by Jai Singh, literally means the ‘instruments
for measuring the harmony of the heavens’. This was the biggest of the five observatories
he built and the only one which is still in use today. In all there are 17 instruments in
the Jantar Mantar comlex. These instruments can be used to calculate, the local time at
Jaipur, up to an accuracy of 2 seconds, and also gives the time in a 24 hour format for all
he days of the year. There are also instruments to measure the lonngitude and latitude of
the celestial bodies, the azimuth (arc of the celestial great circle from Zenith to horizon)
of planetary bodies, the altitude and the azimuth,the angular measurement of an object from
the equator, the precise coordinates of celestial bodies and the sun’s longitude and latitude
and the zodiacal sign that it is passing through.

See the Delhi Jantar Mantar here...