The Astronomical Observatories of Jai Singh c15.s2.2

c15.s2.2

They fully realised the necessity for methodical observation, and, in practical astronomy, they excelled the Hindus and Europeans of their time.¹ The first series of regular observations, with the aid of fairly accurate instruments, appears to have been made at Gondeshāpūr, in the south-west of Persia, in the first years of the ninth century of our era. During the Califiate of al-Ma'mūn (A.D. 813—833), at the observatory at Baghdād, all the fundamental elements of the Almagest were verified—the obliquity of the ecliptic, the precession of the equinoxes, the length of the solar year, etc. A measurement of an arc of the meridian in the region of Palmyra was also carried out during the same period, and similar observations continued to be made throughout the Muslim world until the middle of the fifteenth century. The observatory at Cairo was founded in the tenth century, and the observations there were recorded in the ‘Ḥākimid Tables’ (al-zīj al-Ḥākimī). In Persia an observatory was founded, in A.D. 1074, at Nishāpūr, and there, in A.D. 1118, al-Khāzinī complied his ‘Sanjaric Tables’ (al-zīj al-Sanjari). In 1259 a great observatory was founded at Marāgha in North-West Persia, and there Naṣīr al-Dīn-Ṭūsī (mentioned by Jai Singh), published his famous ‘Ilkhānic Tables.’