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Al-Sufi’s constellations
A 10th-century Arabic astronomer
who kept alive the Ptolemaic tradition
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ALL astronomers know the names of Ptolemy, Tycho Brahe and Johannes Hevelius, three landmark characters who catalogued the stars with ever-increasing accuracy between the second and seventeenth centuries. Less familiar in the West, but no less influential, is the tenth-century Persian astronomer Ἁbd al-Raḥmān al-Ṣūfī (903–986), usually known simply as al-Ṣūfī, or Azophi in Latinized form. Al-Ṣūfī was the Arabic successor to Ptolemy at a time when the Greek tradition in astronomy had died out in the West but was being rediscovered in the Middle East.
Al-Ṣūfī, who worked in the Persian city of Shīrāz (now in Iran) and then in
Baghdad, used the star catalogue in Ptolemy’s Almagest as the basis for his own Arabic version called Kitāb al-Kawākib al-Thābita, i.e. Book of the Fixed Stars. This appeared in or shortly after AD 964, some eight hundred years after the original Almagest was written. Al-Ṣūfī’s book, the first-ever updating of the Almagest, became the standard constellation handbook for several centuries thereafter,
inspiring the development of Arabic astronomy and eventually aiding the
transmission of Greek astronomy back into the West. Al-Ṣūfī was one of the four
ancient authorities credited on the first European printed star charts produced by Albrecht Dürer in 1515.
Like all books in the days before printing, the Book of the Fixed Stars was written and illustrated by hand. Further copies had to be hand-made too,
and each copy was unique and prone to loss or damage. Al-Ṣūfī’s original manuscript has disappeared, but we still have an early copy reputedly
made by his son Ibn al-Ṣūfī and thought to date from 24 years after his father’s death, although some scholars consider it a much later copy by a different
author. One of the treasures of astronomical history, this manuscript is kept
in the Bodleian Library, Oxford, where it is catalogued as Marsh 144; it can be
seen online
here. (No English translation of it has yet been published, but one is in
preparation by Ihsan Hafez of James Cook University, Australia.) Ibn al-Ṣūfī also based a poem about the
stars on the book, thereby helping to popularize his father’s work.
Al-Ṣūfī’s book retained the same 48 constellations and their component stars as in the Almagest, but in the accompanying text he added information about traditional Bedouin
Arabic constellations and Arabic star names. Most of the book consists of
discussions of the constellations and their stars in Greek and Arabic
tradition.
To the casual viewer, the main attraction of the book is the constellation
illustrations, something that the original Almagest notably lacked. Each constellation was depicted twice, first in mirror image, as
it would appear on a celestial globe, and secondly as it actually appears in
the sky.
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The human constellation figures are depicted in Islamic style. One intriguing divergence from the classical Greek iconography is that of Perseus, in which the head of Medusa has become a bearded man. Possibly the Arabs had seen illustrated European manuscripts of the works of Aratus and Hyginus and misinterpreted the streams of blood dripping from the Gorgon’s head as a beard. A detailed study of Arab constellation iconography can be found here.
On the charts of manuscript Marsh 144, the stars that Ptolemy had regarded as
forming a given constellation are drawn as red dots with black labelling, in
some cases including their names; while those stars that Ptolemy listed as
lying outside the main constellation figures – the so-called ‘unformed’ stars – are in black with red numbers. Later copies of al-Ṣūfī’s book used different colour schemes for the stars and labelling.
As well as plotting Ptolemy’s individual stars and three nebulae from the Almagest, al-Ṣūfī inserted more than 40 stars from his own observations. In Marsh 144
these are drawn in black, without accompanying numbers because they were not
part of the star catalogue. Look, for example, at al-Ṣūfī’s chart of Cepheus. The two ‘unformed’ stars that Ptolemy described as lying on each side of the King’s head-dress can clearly be seen in black; but as well as those, al-Ṣūfī has
added another five stars of his own in and around Cepheus’s legs and four more near his elbow.
Each of al-Ṣūfī’s charts was accompanied by a table of stars that closely followed the listing
in the Almagest (for an example of a star table from the Almagest see here.) Al-Ṣūfī repeated Ptolemy’s description of each star’s position in the constellation figure, and he also added Arabic names for the
stars where he knew of them.
The tables give the celestial latitude and longitude of each star for AD 964, the year in which the book was written. These coordinates came not from new
observation but simply by adjusting Ptolemy’s figures by a calculated amount to account for precession. Al-Ṣūfī did, though,
use his own observations to correct the magnitudes of about half the stars in
the lists. None of al-Ṣūfī’s own stars were incorporated into the tables, which were restricted to Ptolemy’s original listings. It is clear that a guiding factor in the book was, as far
as possible, the preservation and continuation of the Ptolemaic tradition.
We can never know how many copies of the Book of the Fixed Stars were made over the years, but over 90 are currently preserved in museums and
libraries around the world. Each has its own individual features, because each
copyist introduced their own version of the constellation figures, influenced
by local style and tradition.
One of the most celebrated copies is one that was made in the 1430s and
originally belonged to the great Muslim astronomer Ulugh Beg (1394–1449). This is now kept at the Bibliothèque Nationale de France and is known as MS Arabe 5036. Working at his own observatory in Samarkand, in modern Uzbekistan, Ulugh Beg reobserved the stars of the Almagest to
produce the Zīj-i jadīd-i Sultānī, published in 1437, the most accurate star catalogue prior to that of Tycho
Brahe, although it lacked the popular appeal of al-Ṣūfī’s illustrated version.
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