Johannes Angelus

The Astrolabium Planum was printed at Augsburg in 1488 under the name of Johannes Angelus, the German astronomer and physician Johann Engel. Most of the volume is working astrological apparatus, tables for dividing the houses and instructions for their use. What has kept it in circulation is a different section: a series of images, one for each of the three hundred and sixty degrees of the zodiac, each with a short accompanying text describing a figure or a scene.

The images are not his invention. Degree by degree image material was already circulating in manuscript and is generally traced back to earlier compilations associated with the name of Pietro d'Abano, itself standing on older astrological sources, and the printed book gathers and fixes what had been variable. That distinction matters for how the atlas cites it. The Astrolabium Planum is the earliest widely available witness to this body of imagery rather than its origin, and a claim that a particular degree image begins here needs checking against the manuscript tradition rather than assuming the printed edition is the source.

A degree image system does a particular job in practice. Ordinary astrological reading works with sign, house and aspect, which are relatively coarse divisions, whereas an image attached to a single degree gives the interpreter something concrete to say about an exact position, and that exactness is the appeal. It is also the weakness. A birth time uncertain by four minutes moves a chart by roughly a degree, so the apparatus depends on a precision the underlying data usually does not support.

The interesting thing about this book is what printing did to it. A manuscript circulating among a few practitioners varies from copy to copy, and no two readers are certainly working from the same text. A printed edition produces hundreds of identical copies, so that everyone consulting the degree images afterwards is consulting the same images in the same order, and the variation that had been normal in the tradition stops. Angelus contribution was the edition, and the edition is what mattered.

The genre continued, and the atlas has to be careful about how the later members relate to it. In 1898 the Welsh astrologer Charubel published a set of symbolic readings for every degree, obtained by his own method rather than compiled from earlier books. In the twentieth century a further and much better known set of degree symbols was produced in California by an entirely separate process and has its own entry in this atlas. All three are degree image systems and none of the later ones is a revision of the earlier. Resemblance of genre is not descent, and treating a family of similar projects as a single transmitted tradition is one of the commonest errors in the history of astrology.

The manuscript question stays open. Which earlier compilations fed the 1488 text, in what order, and how much the editor or the printer altered on the way, would be settled by collating the surviving manuscripts against the printed book, and that work is not available in a form this atlas can cite. It is recorded here as an open question rather than passed over, and carries a matching entry in the atlas register of unresolved questions.