Ibn Yunus

His father was a historian, biographer, and scholar of hadith who wrote two volumes about the history of Egypt—one about the Egyptians and one based on traveller commentary on Egypt.

[6] A prolific writer, ibn Yunus' father has been described as "Egypt's most celebrated early historian and first known compiler of a biographical dictionary devoted exclusively to Egyptians".

[7] His grandfather was also one of the scholars who specialized in astronomy, and Ibn Yunus enjoyed great prestige among the Fatimid caliphs, who encouraged him to pursue his astronomical and mathematical research.

[8] One of his greatest astronomical works was that he calculated with great accuracy the inclination of the ecliptic circle, after observing the solar and lunar eclipses.

For example, he accurately describes the planetary conjunction that occurred in the year 1000 as follows: Modern knowledge of the positions of the planets confirms that his description and his calculation of the distance being one-third of a degree is exactly correct.

Ibn Yunus's observations on conjunctions and eclipses were used in Richard Dunthorne and Simon Newcombs' respective calculations of the secular acceleration of the Moon.

[12][13] Recent encyclopaedias[14] and popular accounts[15] claim that the tenth century astronomer Ibn Yunus used a pendulum for time measurement, despite the fact that it has been known for nearly a hundred years that this is based on nothing more than an error made in 1684 by the Savilian Professor of Astronomy at Oxford Edward Bernard.