The Astronomical Observatories of Jai Singh c15.s2.t1.15

c15.s2.t1.15

The notion of increasing the size of the instrument as far as possible has already been referred to (page 35). It is perhaps to Abu'l Wafā that we owe some of the immense instruments which the Arab works mention. With a quadrant of over 20 feet radius the obliquity of the ecliptic was observed in A.D. 995. The sextant of Abu M. al-Khojendi (C. A.D. 992) was of nearly sixty feet radius. In the tenth century the aperture dial was used, and Naṣīr-al-Dīn, by utilising a hole in the dome of a large building, obtained excellent results. According to Greaves the quadrant used by Ulugh Beg was 180 feet high.⁴