The observatory Jantar Mantar,(roughly translates to “The Formula of Instruments") was built by Sawai Jai Singh II. It consists of fourteen major geometric devices for measuring time, predicting eclipses, tracking stars in their orbits, ascertaining the declinations of planets and determining the celestial altitudes and related ephemerides. Phew!!
Each is a fixed and “focused” tool. The Samrat Jantar, the largest instrument is 90 feet high, its shadow carefully plotted to tell the time of day. Its face is angled at 27 deg; the latitude of Jaipur, the Hindu chhatri (small domed cupola) on top is used as a platform for announcing eclipses and the arrival of monsoons.
Built of local stone and marble, each instrument carries an astronomical scale, generally marked on the marble inner lining.