University of Tehran Researcher Chronicles Traces of Forgotten Astronomers in a Millennium-Old Book
According to the Public Relations Office of the University of Tehran, Al-Zij al-Hakimi al-Kabir (The Great Hakimid Astronomical Tables) was compiled by Abul-Hasan Ali ibn Abd al-Rahman ibn Ahmad ibn Yunus, commonly known as Ibn Yunus, the renowned Egyptian astronomer, toward the end of the 4th century AH (circa 10th–11th century CE). Ibn Yunus based this work on an extensive collection of his own observations as well as those of earlier astronomers—a distinctive feature that sets it apart from many similar works of the period.
In this study, the records preserved in Al-Zij al-Hakimi have not been examined merely as data concerning the motion of celestial bodies; rather, the information contained therein has been utilised to reconstruct a portion of the history of observational astronomy and to recover the contributions and activities of astronomers whose writings have largely been lost. According to the research, the reports pertaining to Mahani, the Amajur family, and Ahmad Nahavandi are among those that, in some cases, constitute the sole extant source for understanding the observations of these scholars.
One of the most significant characteristics of Al-Zij al-Hakimi is the meticulous recording of numerous observational details made by Ibn Yunus and his predecessors. This wealth of information renders the work an invaluable resource for comprehending the astronomical tradition of the 3rd and 4th centuries AH, particularly because a portion of these data relates to observations that are scarcely—or never—recorded in other sources.
The study also presents a different perspective on Ibn Yunus's working methods. Contrary to certain historical narratives that speak of a well-equipped, state-sponsored observatory at his disposal, an examination of Ibn Yunus's own records indicates that his observations were largely conducted in a private setting, employing portable instruments. On some occasions, he also used public venues, such as mosques, for conducting observations or verifying results.
Another noteworthy aspect of this research involves the analysis of solar and lunar eclipse records. In Al-Zij al-Hakimi, Ibn Yunus documented 30 eclipses—comprising 10 solar and 20 lunar events—some of which originated from observations made by earlier astronomers whose original works have not survived. These data were later employed, from the mid-18th century CE onward, in studies concerning long-term variations in the Moon's motion.
In a further section of the paper, the reports on planetary observations and the compilation of data regarding celestial motion are examined. According to the study, the accuracy of Ibn Yunus's observations, combined with his use of earlier astronomers' data, contributed to the production of more precise astronomical tables. Relying on these data, he was able to identify certain errors present in earlier calculations and observations, including those attributed to Ptolemy.
To supplement and, in some instances, correct the reports found in Al-Zij al-Hakimi, the study also draws on the writings of other scholars, particularly the accounts of Abu Rayhan al-Biruni. This comparative approach across various sources has facilitated a more rigorous examination of the scattered information concerning the history of observational astronomy in the early Islamic centuries.
One of the salient points of the research is its attention to reports on Iranian observations and astronomical activities in regions such as Jundishapur, Samarkand, and Nishapur—data which, according to the author, are not recorded in this form even in some of the extant works of al-Biruni. From this perspective, Al-Zij al-Hakimi is not merely an astronomical treatise; it stands as a crucial document for studying the history of science and the transmission of astronomical knowledge across the Islamic world.
The article, titled "The History of Observational Astronomy up to the 4th Century AH as Narrated by Al-Zij al-Hakimi al-Kabir and Its Parallel Texts", is authored by Dr. Younes Karamati and has been published in the journal History of Science (Volume 23, Issue 2), published by the University of Tehran Press.
The article can be accessed via the following link:
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