The Astronomical Observatories of Jai Singh c10.50

c10.50

On the east wall of the building is a graduated semicircle called Dakṣiṇo vṛtti Yantra, used for obtaining meridian altitudes. The north wall of the Miśra Yantra is inclined to the vertical at an angle of 5 degrees (figure 51), and is marked with a large graduated circle. This is called the Karka Rāśi Valaya, or ‘Circle of the sign of Cancer.’ As the latitude of Delhi observatory is 28° 37′ 35″, and the obliquity of the ecliptic is 23° 27′ 5″ nearly, the zenith distance of the sun, when in Cancer, is 5° 10½′, approximately, and the sun then shines over the north wall for a short period, and the shadow of the centre pin falls on the graduated circle. This may be the northern dial referred to by Jagannāth (see page 39).