Though we pay no heed to Ptolemy’s geometry today, his Star Catalogue remains the heart of the modern northern sky. Almagest VII.v – VIII.i presents a listing of more than a thousand stars, a map of the sky as visible from Mediterranean latitudes.
In Almagest VII.iv, Ptolemy describes briefly how the positions of the stars were measured in reference to the ecliptic. He makes it clear that his starlist is based upon a preexisting catalog of stars, but notes that he’s made a few edits to the star descriptions, “as, for example, when those stars which Hipparchus places in the shoulders of the Virgin, we call her sides because their distance from the stars in the head appears greater than that from the hands.” (RCT translation)
The star descriptions of Ptolemy’s Catalogue often seem fanciful; yet, while they might have been rooted in folk traditions, Ptolemy’s descriptions were not a whim of fancy, but a scientific standard for two thousand years or more. ‘The left hand of the virgin’, or ‘the second of three in the tail of the bear’, or ‘the star in the heart of the lion’ – these might have derived from folk tradition, but by Ptolemy’s day they were standards, recognized internationally by those who recognize international standards. (International standards are funny that way.)
There may have been other starlists in circulation, but that of Ptolemy became a standard, as copies of this Catalogue circulated separately from the rest of the Mathematical Treatises. Few astrologers would want to learn to craft a personal ephemeris, but most would want a copy of a tabulation of the stars, to help them interpret ephemerides purchased from mathematical adepts. As Mesopotamian astrology spread beyond the Mediterranean, Ptolemy’s stars became a scientific standard around the Mediterranean, spreading north and west into Europe, and east into western Asia.
The constellations of Ptolemy’s Catalogue remain today a framework for the stars of the northern sky.
In the Reading Room [LINK] we have some copies of this Catalogue.
If you’d like to try to identify the stars that Ptolemy lists, a crude scan of the Catalogue from the unannotated translation of R.C. Taliaferro is provided [LINK]. (We have reached out to Britannica for permission to post this material; no reply. We hope that they’ll provide a cleaner pdf copy.)
If you’d prefer an annotated version, we’ve also posted a copy of a 19th century work by Peters & Knobel [LINK], which identifies the stars of Ptolemy’s catalogue by their Bayer designations. (This work is long out of copyright, and free to distribute. Give thanks to librarians around the world who are capturing digital copies of public-domain texts like this, and making them easily available.)
The text of Manitius [LINK; auf Deutsch] is also in the public domain.
The more recent translation of the Catalogue of Almagest by G.J. Toomer is fully annotated, relying on (and occasionally correcting) both P&K and Manitius. In our investigations, we’ve found a few occasions to correct GJT; but we’ve got access to software tools that he did not. We’ll be reaching out to Princeton University Press for permission to post or link to a copy of books VII – VIII.
(We would encourage Princeton University Press to print an updated edition, with new figures. At the time that GJT’s edition was crafted, computer graphics were in a nascent stage. Your author had personal experience with X-Y plotters of the late ’70s / early ’80s, and remembers a brief period when figures such as those of GJT were cutting edge. Yes, really. With tools available today, an undergraduate summer intern could easily produce figures vastly surpassing these. Indeed, the illustrator of the Britannica / RCT edition did far better work with tools and skills of the 1940s.)