Al-Sufi seems rather hard on Al-Battani (or Albategnius as he is usually called) for he is generally considered to have been the most distinguished of the Arabian astronomers. His real name was Mohammed Ibn Jaber Ibn Senan Abu Abdallah Al-Harrani. He was born about A.D. 850 at Battan, near Harran in Mesopotamia, and died about A.D. 929. He was the first to make use of sines instead of chords, and versed sines. The _Alphonsine Tables_ of the moon's motions were based on his observations. After some severe criticisms on the work of Al-Battani and Atârid, Al-Sufi goes on to say that the other class of amateurs who desire to know the fixed stars follow the method of the Arabians in the science of _Anva_[392] and the mansions of the moon and the books written on this subject. Al-Sufi found many books on the _anva_, the best being those of Abu Hanifa al-Dînavari. This work shows that the author knew the Arabic tradition better than any of the other writers on the subject. Al-Sufi, however, doubts that he had a good knowledge of the stars themselves, for if he had he would not have followed the errors of his predecessors. According to Al-Sufi, those who know one of these methods do not know the other. Among these is Abu-Hanifa, who states in his book that the names of the twelve signs (of the Zodiac) did not originate from the arrangement or configuration of the stars resembling the figure from which the name is derived. The stars, Abu-Hanifa said, "change their places, and although the names of the signs do not change, yet the arrangement of the stars ceases to be the same. This shows that he was not aware of the fact that the arrangement of the stars does not change, and their mutual distances and their latitudes, north and south of the ecliptic, are neither increased nor diminished." "The stars," Al-Sufi says, "do not change with regard to their configurations, because they are carried along together by a physical motion and by a motion round the poles of the ecliptic. This is why they are called fixed. Abu-Hanifa supposed that they are termed fixed because their motion is very slow in comparison with that of the planets." "These facts," he says, "can only be known to those who follow the method of the astronomers and are skilled in mathematics." Al-Sufi says that the stars of the Zodiac have a certain movement following the order of the signs, which according to Ptolemy and his predecessors is a degree in 100 years. But according to the authors of _al-mumtahan_ and those who have observed subsequently to Ptolemy, it is a degree in 66 years. According to modern measures, the precession is about 50"·35 per annum, or one degree in 71½ years.