 Subsequently, Al-Sufi mentions the same values in his Book of Fixed Stars, that Ptolemy's value for precession is 1 degree per 100 solar years.He then quotes a different value from Zij Al Mumtahan, which was done during Al-Ma'mun's reign, as 1 degree for every 66 solar years.He also quotes the aforementioned Al-Battani's Zij Al-Sabi' as adjusting coordinates for stars by 11 degrees and 10 minutes of arc to account for the difference between Al-Battani's time and Ptolemy's.