The Astronomical Observatories of Jai Singh c11.s2.t1.5

c11.s2.t1.5

Rāśi Valaya Yantra.—The Rāśi Valaya, or ‘ecliptic instrument,’ consists of a collection of dials, situated on a platform to the west of the Samrāṭ Yantra (Plate XXI and figures 54 and 55). There are twelve such dials, one for each sign of the zodiac (that for Capricornus is seen in figure 55), and each instrument is exactly of the same type as the Samrāṭ Yantra, but the quadrants lie, not in the plane of the equator, but in the plane of the ecliptic when the particular sign is on the horizon, and the edge of the gnomon then points to the pole of the ecliptic; consequently, at the proper moment the instrument indicates the sun's latitude and (with appropriate graduations) longitude. The radius of the quadrant is 5 feet 6 inches in the case of four instruments, and 4 feet 1¼ inches in the case of the other eight. The contemporary lists do not mention the Rāśi Valaya.