Al-Zarqali Western Arabian astronomer and mathematician Date of Birth: 01.01.1029 Country: Spain

1. Arsachel: The Astronomer and Mathematician
2. Life and Career
3. Astronomical Discoveries
4. The Toledan Zij
5. Lunar Legacy
6. The Shape of Planetary Orbits

Arsachel: The Astronomer and Mathematician

Born in Al-Andalus (present-day Spain), Abū Isḥāq Ibrāhīm al-Zarqālī, also known as Arsachel, was a prominent astronomer and mathematician of Jewish descent during the 11th century.

Life and Career

Initially a craftsman specializing in astronomical instruments, Arsachel eventually became a renowned astronomer himself. He resided in Toledo, then part of Al-Andalus, until the city's reconquest by the Spanish in 1085, after which he moved to Seville.

Astronomical Discoveries

Arsachel made significant contributions to astronomy. He invented the "zarqala" astrolabe, which projected the celestial sphere onto the plane of a great circle passing through the poles of the world and the solstices. This instrument, also known as the "saphaea Arzachelis," gained popularity in Europe.

The Toledan Zij

Arsachel compiled the "Toledan Zij," a set of astronomical tables known as the "Canon Arzachelis in the Toledo Tables" in Western Europe. He is also credited with designing the "Equatorium," an astronomical instrument.

Lunar Legacy

In recognition of his astronomical achievements, a lunar crater bears the name "Arzachel."

The Shape of Planetary Orbits

While studying the motion of Mercury, Arsachel observed that the center of its epicycle traced an oval shape rather than a circle as proposed by Ptolemy's theory. This observation was not a direct anticipation of Kepler's first law on elliptical orbits, as Arsachel remained rooted in the geocentric model and made no reference to ellipses in his calculations.