Historical Context The treatise was written in the Persian city of Shiraz, for the patron and Buyid emir ‘Abud al-Dawla. Although al-Sufi made his longitudinal calculations correct for the year 964 only, the work remained highly influential, functioning as the standard text on Arabic astronomy to be consulted in all Islamic territories and faithfully copied for many centuries after its production. Since it was only correct for the single year of 964, the Book of Fixed Stars was intended to serve a broader educational purpose, rather than being concerned with the mathematical technicalities of astronomy. The Book of Fixed Stars is representative of the concerns of Islamic scholars during the late-9th to 11th Centuries AD, where following the translation of Hellenistic texts from Greek to Arabic, “Islamic astronomers and astrologers concentrated on analyzing, criticizing, and perfecting the geometrical models of Ptolemy.” Medieval Islamic astronomers also drew from Sanskrit and Middle Persian sources to learn "methods for calculating the position of heavenly bodies, and for creating tables recording the movement of the sun, the moon, and the five known planets." In the context of this shift to observational and theoretical astronomy set in motion by the translation movement, and with al-Sufi himself being an observational astronomer, the Book of Fixed Stars comprises an important organisation and revision of classical knowledge from antiquity (the first of its kind), and some of the earliest surviving examples of visual documentation of celestial bodies observable by the naked eye. The interest in cataloging the stars also stems from the nature of worship in Islam. The religion requires that its members are able to locate Mecca so that they may pray in the right direction, and to also be able to determine the correct times for prayer. In addition to the daily requirements, during the festival of Ramadan they must also know the moments of sunrise and sunset for fasting, and the fixed location of the moon for the start of each new month. The Book of Fixed stars also marks a trend of an increased production of illustrated manuscripts, as it is one of the oldest surviving treatise of its kind. This is not to say that this text was the first illustrated manuscript ever created, as there are many illustrated fragments that have been found and studied, most notably the Fustat fragments. The Fustat Fragaments are illustrated scraps of parchment that were found during excavations in Fustat, or Old Cairo. These fragments can be attributed to the stylings of the Fatimid period (969-1171), therefore dating the existence of astronomical illustrations to many years before the creation of The Book of Fixed Stars. The increase in illustrated manuscripts is also related to the advent of paper in the Islamic world in the tenth century. The increased availability of this material, which was much cheaper than the previously used parchment, drove the production of books in the Islamic world. Contents The book was thoroughly illustrated along with observations and descriptions of the stars, their positions (copied from Ptolemy's Almagest with the longitudes increased by 12° 42' to account for the precession), their magnitudes (brightness) and their color. Notably, al-Sufi improved upon Ptolemy's system for measuring star brightness. Instead of two brightness categories (‘more bright’ and ‘less bright’), al-Sufi employed three: AṢghareh (‘less’), Akbareh (‘greater’), and A’ẓameh (‘much-greater’). Ihsan Hafez has recorded 132 stars in al-Sufi's work not mentioned by Ptolemy. Al-Sufi's results, as in Ptolemy's Almagest, were set out constellation by constellation. For each constellation, he provided two drawings, one from the outside of a celestial globe, and the other from the inside. Al-Sufi's reasoning for this was that ‘the beholder might be confused if he saw the figure on the globe differing from what he sees in the sky’, demonstrating the book's use as a teaching device.[14] Persis Berkelamp argues that each paired constellation was drawn slightly differently to encourage students to study the manuscript closely. Introduction In his introduction, al-Sufi dedicates the work to his patron 'Abud al-Dawla and outlines the sources he has used to write the book. These sources, including a number of treatises and objects which are now lost, serve as important indicators and records of the knowledge ('ilm) production at the time. For instance, the introduction lists the names of 3 authors (Ibn Kunasa, Ibn al-'Arabi, Abu Hanifa al-Dinawari) and their treatises concerning pre-Islamic Bedouin traditions, all of which are now lost. Chapters The Book of Fixed Stars follows the 48 Ptolemaic constellations described in the Almagest, with a chapter dedicated to each individual constellation. Each chapter is split into 4 subsections. Ptolemaic constellations Each chapter begins with a description of the specified constellation and the stars that make up each grouping, thus departing from the Almagest and its concern for describing the iconographical origins of each constellation outline in Greek mythology.[17] Here, al-Sufi is often critical of Ptolemy for seemingly prioritising the constellation outline over the actual stars in a constellation grouping, with some stars being overlooked. In making these revisions, al-Sufi was able to determine the boundaries for each constellation's star grouping. Indigenous Arabic constellations Al-Sufi continues his description of the specified constellation in terms of the Pre-Islamic Bedouin constellations and star groupings, noting their positions and distance to the Ptolemaic constellation stars. Illustrations In this section, al-Sufi presents 2 different views/illustrations of the specified Ptolemaic constellations: the constellation viewed in the sky from the ground and the constellation as viewed on top of a globe. The latter view can be explained by accounts of al-Sufi's drawing process, whereby the author carefully fitted a thin sheet of paper on top of a celestial globe and then directly copied the constellation outlines and star positions from the engravings. The inclusion of this globe view of each constellation also suggests that the Books of Fixed Stars was intended to be used by owners of celestial globes, and many surviving globes from the 13th and 14th Centuries include statements attesting to the treatise as an influential source. Although al-Sufi names several sources in his introduction which contributed to the book's illustrations, none of these treatises nor celestial globes survive. These illustrations represent another important departure from the Almagest which does not include any illustrations. Star Catalogue The book includes a comprehensive catalogue of the individual stars, modified and extended from that of the Almagest, and including revised star magnitude values.