The Astronomical Observatories of Jai Singh c6.s1.t1.19

c6.s1.t1.19

*Ankabut co-ordinates.*—On the other side of the ‘tablet of the horizons’ is generally the ‘tablet of the latitude of the complement of the total obliquity.’ This really gives the celestial co-ordinates (longitude and latitude) and by its aid the positions of the stars on the ‘ankabūt can be at once read off. Morley seems to have thought ² that this was an ordinary tablet for latitude 66½° N, but it is quite rightly described as *Ṣafīḥah mīzān al-‘ankabūt*, ‘the tablet of the measure of the ‘ankabūt.’ It occurs in most of the astrolabes I have examined.