Analyzing the Great Comet of 1471-2. The First Scientific Astronomy Book Printed during its Author’s Lifetime.

Schleusinger, Eberhard (ca. 1430-1488)

De cometis anni 1472

Venice: Hans Aurl, 1474

$85,000.00

Quarto: 21.7 x 16 cm. [34] lvs. Collation: [i]12, [ii]10, [iii]12. Complete with the initial and terminal blanks.

FIRST DATED EDITION.

One of only two 15th c. editions. The priority of the editions is unresolved but this is generally considered the second (see below.) Bound in contemporary blind-ruled calf over thick wooden boards with small metal bosses. Lacking the single clasp but retaining the upper catch plate. The text is extremely fresh, with generous margins; the impression of the type is deep and clear. With manuscript waste guards inserted in the three quires. The text block has been re-attached to the binding but there is no indication that this is a remboîtage. Extremely rare. 5 copies in North America (The Walters, LC, NYPL, Yale Medical, The Morgan.)

The exceedingly rare first dated edition of one of the two earliest astronomical treatises on comets. This work is distinguished from the other by not only recording observations but also containing mathematical calculations to determine the size of the comet and its distance from the earth, making it the first printed book by a living author to employ pure science in the investigation of an observed natural phenomenon.

On Christmas 1471, a huge comet appeared over Europe and remained clearly visible until March of the following year. The celestial object was observed by several humanist scholars, including Regiomontanus, and sparked interest not only in the usual fields of prophecy and prognostication, but also stimulated true scientific interest. This is one of only two contemporary accounts of the comet to appear in print. The other (ISTC ic00287600), by Angelo Catone Supinas of Benevento, was printed at Naples by Sixtus Riessinger, after 1 Mar. 1472. However, unlike the work offered here, the Naples work does not include any scientific calculations.

The anonymously-published work (the author is only identified as a “Doctor of Zurich”) is attributed to the physician and mathematician Eberhard Schleusinger, a student of Georg Peurbach and a colleague and friend of Regiomontanus. Internal evidence suggests that Schleusinger wrote his work after April 1472 and before 1473, a year for which he formulated some predictions. The short treatise appeared in print in Beromünster, near Luzern, in an undated edition by Helias Heliae, who died in 1475, after printing “de Cometis” and six other books on non-scientific topics. 

The colophon of the present edition bears the year 1474. A comparison with the presumed first edition by Heliae reveals differences that suggest that Aurl’s edition was composed from a manuscript source rather than a copy of Heliae’s edition. The exact relationship of the two remains a matter of active investigation.

There is, however, little doubt that this edition was produced in Venice. The Typenrepertorium der Wiegendrucke classifies the type used as 1:119R and assigns it to the press of Florentius de Argentina, who was active in Venice around 1472. In the 1470s, Venice became the main European center of early astronomical publishing, even more so after the rapid collapse of Regiomontanus’s ground-breaking private press in Nuremberg.

“Comet C/1471 Y1 (discovered on 25 Dec 1471) is unique among bright comets of modern times because no brighter comet has come so close to Earth. On 22 January, 1472, the separation was just 10 million kilometers. Since then, only the great comet of 1556 and Hyakutake in 1996 reached a somewhat comparable value but neither came so close to our home planet.

“The period of visibility was restricted to the time before perihelion on 1 March 1472. The comet first appeared in the constellation Virgo in the morning sky at the end of December 1471. From there it moved on a generally northerly path into Boötes, passing Arcturus, and into Coma Berenices.

“At the end of January 1472, the comet reached Ursa Major, and was visible for the whole night from Central Europe. On the 22nd it passed the North Celestial Pole at a distance of 15 degrees. Its closest approach to Earth occurred the following day. At this time the comet was moving faster than 1 degree per hour and within 24 hours had passed from the spring constellations to the autumn ones. However, the full Moon on 27 January affected its visibility.

“At the end of January, the comet moved back towards the south. It was now an object in the evening sky and was passing through the autumn constellations. There, it disappeared in Cetus around the time of perihelion. Passage past the Sun followed shortly after on 11 March. No observations were recorded after perihelion.

“Eberhard Schleusinger from Bamberg took the Great Comet as an opportunity to carry out a distance determination. He did this starting from the Earth’s circumference as being 913 German miles (Meilen) and the distance of the Moon as being 33 times that value. He determined the distance of the comet from a daily observation of its motion relative to the star Spica. From a value of 6 degrees, he calculated the distance as 8,200 Meilen (equivalent to about 62,000 km) which for him confirmed the Aristotelian view that comets were not objects within the outer fiery spheres but instead belonged to the sub-lunar region influenced by the Earth. Regiomontanus, who became famous through his tables of ephemerides for navigators, accepted Schleusinger’s calculation.”(Stoyan, Atlas of the Great Comets (2015), p. 49-50) Schleusinger also measured the tail to be 35 degrees, corresponding to a length of more than 4,000 miles.

Schleusinger was born around 1430, probably in Lower Bavaria. He studied medicine and ‘artes liberales’ at Vienna, where he received his doctorate and became the personal physician of the bishop of Bamberg. Between 1472 and 1488 he was in Zurich, where he worked as a physician. The year of his death is not known. 

It was in Vienna that Schleusinger came under the influence of Georg Peurbach, who also observed the comet. “Schleusinger had become Master artium in 1455 at Vienna; hence, he was a member of Peurbach’s Viennese School, and this is manifest in his derivation of the distances and sizes of comets. Progress was unmistakable, whereas Peurbach had only estimated the [1472] comet’s distance, Schleusinger attempted to determine its parallax, and hence its distance, by measuring distances to a nearby star. 

“[Schleusinger’s work] merits a higher status than the usual writings on comets, with their astrological readings, or Martin Ilkusz’s [unpublished] work, in which he also tried to determine the size and distance of the comet of 1472.”(Zinner & Brown, Regiomontanus: His Life and Work., p. 132.)

It was through Peurbach that Schleusinger met Regiomontanus, who also made observations (now lost) of the 1472 comet. However, at the time of his death, Regiomontanus had manuscript copies of Schleusinger’s calculations among his papers. These were mistakenly taken to be Regiomontanus’ own and were published under his name by Jacob Ziegler in 1548.

The text:

The book is divided into two parts. The first part concerns comets in general and includes discussions of the types of comets (Ch. 3-4), an explanation of how comets are formed, touching on the similarities between their generation and the development of gems, metals, and stones within the earth; their motion (Ch. 5), shape, color, and mass Ch. 6), the categories of comets (based on location, color, and shape), etc. 

In Chapter 10 “How to determine the size of comets”, Schleusinger gives the calculation that he will use in Part II to calculate the diameter of the comet of 1471/2. This first part concludes with numerous chapters on the effects of comets on the physical and mental health of humans and the duration of those effects.

The second part includes a response to an unnamed contemporary who also observed the comet and who believed that the comet moved like Mars in its epicycle, an assumption that Schleusinger, who did not believe in planetary epicycles, refutes.

In  Part II, Chapters 3 and 4, Schleusinger describes the motion of the comet (speed and direction) and the changing orientation of its tail.  It is in Chapters 5, 6 and 7 that Schleusinger makes his important calculations (discussed above) to determine the comet’s distance from Earth, its diameter, and its longitude. He then describes its form and color. Following the format of the first part, Schleusinger concludes his tract with prognostications.

To stress the scientific nature of his book, the author opens with a plea against amateurs and improvised astrologers: “According to Aristotle, no one is a good judge of things that he does not know ... And the ignorant should keep their foolishness hidden instead of flapping their mouths, so that their ignorance is not revealed. And even if they are experienced and learned in many things, yet they are ignorant in the things that are described below, of which they cannot be judges and arbitrators.” The passage was later used by Lichtenberg to reiterate the same notion in his Prognosticatio.” (Green, Printing and Prophecies, p. 64) 

On the question of authorship, see Meyer, Wilhelm J., “Wer ist der Verfasser der Druckschrift über den Kometen 1472 ?” in: Archiv des Historischen Vereins des Kantons Bern 39 (1948), p. 249– 254. For a modern German translation, see Stotz and Ruelli, “Eberhard Schleusinger: De cometis – Traktat über den Kometen von 1472. Kritische Edition und deutsche Übersetzung mit Erklärungen,” p. 3.

ISTC ic00785000. GW 7253. HC 15513 . Goff C785. IGI 3105. Klebs 972.2. BMC V 237. BSB-Ink S-203. GW 7253. E. Zinner, Regiomontanus: His Life and Work, Amsterdam 1990, pp. 130-132. Thorndike pp. 359-360. J. Green, Printing and Prophecies: Prognostication and Media Change 1450-1550, Ann Arbor 2012, p. 64. Dibdin, Bibliotheca Spenceriana IV, nos 787-788. Biblioastrology 7169. Jürgen Hamel, Bibliographie der astronomischen Drucke bis 1700, p. 116