Model of astrolabe (Yantra Raj) and altitude circle, scale 1:24, in the Jaipur Observatory

This is one of a series of models made 1884-6, showing the astronomical instruments of the Jaipur Observatory, India. These were exhibited in 1886 at the Colonial and Indian Exhibition, London. Built of masonry the Jaipur instruments were used to accurately measure the position of the Sun, stars, moon and planets. Lacking telescopes these devices used naked eye sights and massive but precise construction. Known as Yantra Raj (astrolabe & altitude circle), they were built and designed under the supervision of Maharajah jai Singh II. Finding European, Islamic and Hindu astronomical tables inaccurate, Singh decided to make his own observations to improve matters. As ruler of Rajastan, he built several observatories starting in 1724 with one near Delhi.