82 A Short History of Astronomy [CH, in. 



Yunos ( 60), and called in honour of their patron the 

 Ilkhanic Tables. They contained not only the usual tables 

 for computing the motions of the planets, etc., but also a 

 star catalogue, based to some extent on new observations. 



An important result of the observations of fixed stars 

 made at Meraga was that the precession (chapter 11., 42) 

 was fixed at 51", or within about i" of its true value. Nassir 

 Eddin also discussed the supposed trepidation ( 58), but 

 seems to have been a little doubtful of its reality. He died 

 in 1273, soon after his patron, and with him the Meraga 

 School came to an end as rapidly as it was formed. 



63. Nearly two centuries later Ulugh J3egh (born in 1394), 

 a grandson of the savage Tartar Tamerlane, developed a 

 great personal interest in astronomy, and built about 1420 an 

 observatory at Samarcand (in the present Russian Turkestan), 

 where he worked with assistants. He published fresh 

 tables of the planets, etc., but his most important work 

 was a star catalogue, embracing nearly the same stars as 

 that of Ptolemy, but observed afresh. This was probably 

 the first substantially independent catalogue made since 

 Hipparchus. The places of the stars were given with 

 unusual precision, the minutes as well as the degrees 

 of celestial longitude and latitude being recorded; and 

 although a comparison with modern observation shews 

 that there were usually errors of several minutes, it is 

 probable that the instruments used were extremely good. 

 Ulugh Begh was murdered by his son in 1449, and with 

 him Tartar astronomy ceased. 



64. No great original idea can be attributed to any of the 

 Arab and other astronomers whose work we have sketched. 

 They" had, however, a remarkable aptitude for absorbing 

 foreign ideas, and carrying them slightly further. They 

 were patient and accurate observers, and skilful calculators. 

 We owe to them a long series of observations, and the 

 invention or introduction of several important improve- 

 ments in mathematical methods.* Among the most 

 important of their services to mathematics, and hence to 

 astronomy, must be counted the introduction, from India, 



* For example, the practice of treating the trigonometrical functions 

 as algebraic quantities to be manipulated by formulae, not merely 

 as geometrical lines. 



