Look up at the winter sky and you are reading Arabic. Aldebaran, the red eye of the bull, is al-dabaran, "the follower," because it follows the Pleiades across the sky. Betelgeuse descends from yad al-jawza, the hand of the central figure of Orion, garbled by a medieval copyist. Deneb, Altair, Vega, Rigel: dozens of the brightest stars carry names that reached Europe through one of the most influential astronomy books ever written, the Book of the Images of the Fixed Stars by the Persian astronomer ʿAbd al-Raḥmān al-Ṣūfī.
Al-Sufi completed it in 964 at the court of the Buyid rulers in Iran. His project was to take Ptolemy's star catalog, already eight centuries old, and check it against the actual sky. He re-measured brightness and positions, corrected errors, and set the Greek constellations side by side with the older star lore of the Arabian Bedouin, who had their own names and pictures for the heavens. Each constellation was drawn twice, once as it appears looking up at the sky and once reversed, as it appears on a celestial globe, so that astronomers could use the book with either.
His book holds some remarkable firsts. He described a "little cloud" in the constellation Andromeda, the earliest known written record of the Andromeda Galaxy, our nearest large galactic neighbor, some two and a half million light-years away. He also mentioned a white patch visible from southern Arabia but not from Baghdad, now known as the Large Magellanic Cloud, more than five centuries before Magellan's voyage. The Moon has a crater named Azophi in his honor, from the Latin form of his name.
The occult side of the sky is here too. The star we call Algol comes from ra's al-ghul, "the head of the demon," because it marks the severed head of Medusa held by Perseus. Algol blinks: its brightness drops noticeably every few days as a companion star passes in front of it. Medieval astrologers considered it the most dangerous star in the heavens, and European tradition kept the name "Demon Star." Al-Sufi's work traveled so far that when Albrecht Dürer made the first printed star charts in Europe in 1515, he drew four astronomers in the corners of the sky, and one of them is labeled "Azophi Arabus."
This page comes from a copy made in the late 15th century, more than 500 years after al-Sufi wrote, which shows how long the book stayed in use. The figures wear the clothing of the copyist's own time and place rather than ancient Greek dress, which is how the old sky kept being made new.
It's a humbling thing to own. The pictures are art, but the dots are data, the patient work of someone who spent nights on a rooftop more than a thousand years ago making sure the sky was written down correctly.
al-Sufi's Book of the Images of the Fixed Stars appears on our: