Abul Hassan Ali Ibn-Abdul Rahman Ibn-Ahmad Ibn-Yunus Ibn-Abdul Al A'laa Al-Sadafy Al-Masry was born in a famous family with a scientific background. His father Abdul Rahman Ibn-Yunus was one of the great historians and orators of Egypt. His grandfather Yunus Abul Alaa' had been a friend of Al-Imam Al-Shafii, and a scholar in the Hadith.
Ibn-Yunus rose to a notable rank at the court of the Fatimid caliph, Al-Aziz Bi Allah, and his son Al-Hakim Bi-Amr Allah. The caliph built an observatory for him, on the Moqattam Hills, so that he could perform his astronomical researches. He wrote a summary of ephemerises (atronomical tables) in his large ephemeris, known as the Al-Hakimi Ephemeris, "Relating it to Al-Hakim Bi-Amr Allah," despite the fact that he had started it in the time of Al-Aziz Bi-Allah.
Because of his efforts in that field, he became famous throughout the ages as a brilliant astronomer. He observed an eclipse of the sun in the year 358 after Hijra /AD 977 and again in 368 after Hijra /AD 987. These two eclipses were recorded with precision using purely scientific methods. He was responsible for some very sophisticated spherical trigonometry, and his name has been associated with some large instruments, such as an enormous sphere.
His most famous work is the Al-Hakimi Ephemeris. Ibn-Khalkan says that it was written in four large volumes, and although there were many ephemerises; his ephemeris had the greatest content.