The Astronomical Observatories of Jai Singh c12.s1.29

c12.s1.29

Bhāskara also mentions Ujjain, in several other connexions, as the place of zero longitude, and he gives its latitude as 'one sixteenth of the whole circumference, north of the equator.' This is equivalent to 22½ degrees north, whereas the latitude of the present city is about 23° 11', that of Jai Singh's observatory being approximately 23° 10' 24". Another value was obtained from the length of the equinoctial shadow, which was given as 5 *daṇḍas* 10 minutes, or 310 minutes. This¹ is the shadow of a gnomon 12 *daṇḍas* or 720 minutes high, and hence the latitude= *tan*⁻¹ 310/720 = 23° 17' 40".