Ram Yantra at Jaipur Observatory, India, c 1730.
© Science Museum / Science & Society Picture Library
Model (scale 1:24). This is one of a series of models made between 1884-6, showing the astronomical instruments of the Jaipur Observatory, India. Built of masonry, the Jaipur instruments were used to accurately measure the position of the Sun, stars, moon and planets. They did not have telescopes but used naked eye sights and masive, but precise construction. Known as Ram Yantra ('Altitude & Azimuth instrument'), it was built and designed under the supervision of Maharajah Jai Singh II (1686-1743). Finding European, Islamic and Hindu astronomical tables inaccurate, Singh decided to make his own observations to improve matters. As ruler of Rajasthan he built several observatories, starting in 1724 with one near Delhi.