Abu Jafar Muhammad ibn Husayn Khazin (; 900–971), also called Al-Khazin, was an

Iranian Iranian () may refer to: * Something of, from, or related to Iran ** Iranian diaspora, Iranians living outside Iran ** Iranian architecture, architecture of Iran and parts of the rest of West Asia ** Iranian cuisine, cooking traditions and practic ...

Muslim

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

from Khorasan. He worked on both

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

and

number theory Number theory is a branch of pure mathematics devoted primarily to the study of the integers and arithmetic functions. Number theorists study prime numbers as well as the properties of mathematical objects constructed from integers (for example ...

. Al-Khazin was one of the scientists brought to the court in Ray, Iran by the ruler of the

Buyid dynasty The Buyid dynasty or Buyid Empire was a Zaydi and later Twelver Shi'a dynasty of Daylamite origin. Founded by Imad al-Dawla, they mainly ruled over central and southern Iran and Iraq from 934 to 1062. Coupled with the rise of other Iranian dyn ...

, Adhad ad-Dowleh, who ruled from 949 to 983. In 959/960, Khazin was required to measure the

obliquity of the ecliptic In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbital ...

by the

vizier A vizier (; ; ) is a high-ranking political advisor or Minister (government), minister in the Near East. The Abbasids, Abbasid caliphs gave the title ''wazir'' to a minister formerly called ''katib'' (secretary), who was at first merely a help ...

of Ray, who was appointed by ad-Dowleh. One of Al-Khazin's works ("''Tables of the Disks of the Astrolabe''") was described by his successors as the best work in the field and they make many references to it. The work describes some astronomical instruments, in particular an

astrolabe An astrolabe (; ; ) is an astronomy, astronomical list of astronomical instruments, instrument dating to ancient times. It serves as a star chart and Model#Physical model, physical model of the visible celestial sphere, half-dome of the sky. It ...

fitted with plates inscribed with tables, and a commentary on the use of these. A copy of this instrument was made, but it vanished in Germany during World War II. A photograph of this copy was taken and examined by the historian David King in 1980. Al-Khazin also wrote a commentary on the Roman

polymath A polymath or polyhistor is an individual whose knowledge spans many different subjects, known to draw on complex bodies of knowledge to solve specific problems. Polymaths often prefer a specific context in which to explain their knowledge, ...

Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...

's ''

Almagest The ''Almagest'' ( ) is a 2nd-century Greek mathematics, mathematical and Greek astronomy, astronomical treatise on the apparent motions of the stars and planetary paths, written by Ptolemy, Claudius Ptolemy ( ) in Koine Greek. One of the most i ...

'' in which he gives 19 propositions relating to statements by Ptolemy, and proposed a different model of the cosmos.

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