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Book of the Month

August 1999

Johannes Regiomontanus: Calendar

Printed in Venice by Erhard Ratdolt, 9 August 1482

Euing BD7-f.13

with Sacro Bosco's Sphaera mundi, Alchabitius' Libellus isagogus and Ibn Ezra's De luminaribus et diebus creticis bound in

The solar eclipse of August 11, the recent anniversary of thirty years since the first man stepped on the moon, plus our increasing calendrical obsession as the new millennium approaches, makes our first book of the month - a volume of four astronomical works bound together - a particularly apt choice.

Instrument with two moveable volvelles to show the motion of the moon

Printed calendars and almanacs became extremely popular in the fifteenth century and provided ordinary people with the basic knowledge required to plan their daily routines. The market for calendars was first tapped by Gutenburg, who published a calendar which calculated the times of new and full moons and planetary positions, with readings every two to three days. All earlier calendars, however, were superseded by those of Regiomontanus (1436-1476) whose calculations were far more accurate; he recorded several eclipses of the moon and his interest led him to make the important observation that longitude at sea could be determined by calculating lunar distances. Outstanding also is his observation of a comet in 1472, 210 years before it was "first" seen by Halley.

One of the foremost scholars in mathematics and astronomy during this period, Regiomontanus was professor of astronomy at the University of Vienna before being appointed astronomer to King Matthias Corvinus of Hungary. With funds from his patron and fellow scientist Bernard Walther, he built an observatory in Nuremberg in 1471, and in 1472 erected his own private press in order to publish his discoveries satisfactorily. One of the first to realize the impact printing would have in disseminating scientific knowledge, Regiomontanus' printing output included the first edition of his Calendar. His press was maintained until 1475 when he was summoned to Rome by Pope Sixtus IV to assist in the reform of the Calendar; his death at the age of 40 a year later brought his work to a premature end, a great loss to the developing science of astronomy.

Opening page of Calendar

The elegant edition of the Calendar displayed here was published by Erhard Ratdolt in 1482, some ten years after the original. Between 1474 and 1500 no less than 14 editions of the Calendar were printed in Latin, German and Italian versions: obviously the demand for such works was great. Ratdolt printed his first version of the Calendar in 1476 - a book famous for boasting the earliest known example of an ornamental title-page. This edition of 1482 includes a different but equally lovely title-page with an intricate decorative border. Throughout the book there is an extensive use of beautiful wood-cut initials: the initial "H" shown here is printed in red and white as befits its prominent position on the opening page, but those in the text have white ornamentation upon a black background, a design whose excellence would later influence William Morris.

Ratdolt was a great master printer from Augsburg. In 1482, Venice was the capital of Italian printing and Ratdolt was one of many German immigrant printers who took advantage of the city's established trading position and thriving intellectual scene to set up highly successful printing businesses. As well as producing artistically beautiful books, his firm produced items which were technically innovative. Considering that the art of printing had only been established for some thirty years by this time, his achievements are remarkable.

Imprint details from verso of title-page

Ratdolt further broke with tradition in this book by including the imprint details - that is, the information which tells us when and by whom the book was printed - at the end of the opening verses on the verso of the title-page, rather than at the end of the book in the colophon as was the usual practice.

Data on August from calendar section

As intimated by its title, a large body of the text is taken up by a monthly calendar. This is a Gregorian calendar, of the type still in use today in many countries, which correctly calculates Easter dates. The data for each month is printed on a two-page opening: the astronomical information for the years 1475, 1494 and 1513 is found on the left hand page, while the almanack which includes the names of the chief fasts and festivals is on the facing page. The principal feasts are printed in red, thus making them "red letter days". As can be seen here, dates in the calendar have been personalised by its original owner.

Two pages from the section describing eclipses of the sun and the moon

The book contains much besides the calendar proper. The pages displayed here are from an 8 page section which thoroughly details the times and durations of solar and lunar eclipses. Printing, with its allied art of woodcut illustration, meant that for the first time authors could rely on exact illustrations to convey their ideas sensibly and practically - demonstrated here by the simple diagrams of the eclipses predicted for the years 1483-1530. Each eclipse is depicted by a different woodcut to portray the extent of the obscuration, with the bright portion of the disc in the case of partial eclipses being represented in red. Ratdolt was undoubtedly one of the first printers to introduce the use of coloured astronomical diagrams. The new art of printing was in fact integral to scientific progress and discovery. For example, although the calculations and observations Regiomontanus made in this Calendar are valid only for the location he made the observations from, he also included a tabula regionum - a table of selected latitudes and time allowances, which enabled the data to be corrected to apply to different locations. Thus, the Calendar could aid navigators enormously in gauging their positions accurately from calculating the altitudes of the stars and planets before and after the eclipses. Columbus used a book similar to this in making his first journey to the Americas in 1492.

Instrument with brass pointer to tell the hour

Other information included in the Calendar are charts for daylight hours and seasonal locations of the sun in the sky, phases of the moon, and conversions of planetary hours to equal hours. The text includes an essay on the true date of Easter, with a table indicating the incidence of the festival for each year from 1477 to 1531. The book concludes with 4 pages stuck together to form instruments: the Instrumentum horarum inaequalium, the Instrumentum veri motus lunae with two rotating moveable superimposed discs held to the page by a piece of string ("volvelles"), the Quadrans horologii horizontalis and the Quadratum horarium generale with a brass pointer, displayed here. The ingenuity of the instruments is a further demonstration of Ratdolt's technical skill in overcoming the challenges posed by early scientific publishing. That the instruments are still intact and in working order today is a telling reminder of the superior methods of book production in use 500 years ago.

Diagram showing eclipses of the moon and the sun from Sacrobosco's Sphaera mundi

Throughout his career, Ratdolt displayed a partiality for printing books on astronomy and the mathematical sciences. While the new art of printing resulted in a high output of contemporary scientific books, demand led to many older works also being published. Bound in after our copy of Regiomontanus' Calendar is this astronomical treatise by Johannes de Sacro Bosco, or John of Holywood (c.1195-1256), also printed by Ratdolt in Venice in 1482. Originally written in 1220, the Sphaera mundi is an elementary discourse on the theoretical mechanism of the Universe based on Sacro Bosco's understanding of the ancient Greeks; it was widely used throughout Europe from the middle of the 13th century and was still a standard astronomy text until the 17th century, despite Regiomontanus and other astronomers refuting many of its claims.

Illustration from the moon section in Puerbach's Theoricae novae planetarum

Ratdolt's Sphaera mundi is in fact a collection which contains two further works: Georgius Puerbach's Theoricae novae planetarum and another work by Regiomontanus Disputationes contra Cremonensia, a controversial dialogue on the faults of Cremonensis' work on astronomy. The Puerbach is illustrated by numerous beautiful wood-cut diagrams, several of which are hand coloured.

Opening page of Alchabitius' Libellus isagogus

In the one year 1482, Ratdolt issued no less than 8 works, several of which are amongst his most outstanding productions. His fame, for instance, largely rests in the 1482 first edition of Euclid's Elements: its illustration by over 420 perfect geometrical figures making this another landmark publication.

The third item bound in Euing BD7-f.13 is a less well-known example from Ratdolt's 1482 oeuvre. The Libellus isagogicus is an astrological work, first printed in Mantua by Johann Vurster in 1473. It is not unusual to find works on astrology rubbing shoulders with those on astronomy, since distinctions between the two sciences were somewhat blurred at this time. The opening page displayed here shows several of Ratdolt's trade marks - the printing in black and red, the complicated table, and the ornamental initial letter "P".

The final work bound in this interesting volume is De luminaribus et diebus creticis by the Biblical commentator and astronomer Abraham ben Meir ibn Ezra (1092/3-1167). This was printed in Padua by Matthaeus Cerdonis, also in the year 1482. A short work, its margins are particularly heavily annotated with remarks and observations in Latin.

The book was bequeathed to Glasgow University in the collection of William Euing in 1874 and now bears the class mark Sp Coll BD7-f.13.

Other items of interest

Published by Ratdolt: first edition of Euclid's Elements lavishly illustrated with geometrical figures Sp Coll Hunterian By.2.12 and Sp Coll BD9-c.5 (Venice: 1482); Mataratius' De componendis versibus hexametro et pentametro opusculum Sp Coll BD7-e.5 (Venice:"1468" [ie. 1482]); Eusebius Chronicon Sp Coll BD7-e.3 (Venice: 1483); Publicius Oratoriae artis epitoma with numerous woodcuts including a series of mnemonical diagrams of initial letters Sp Coll BD7-f.18 (Venice: 1485); another copy of Sacro Bosco's Sphaera mundi (Venice: 1485) Sp Coll Hunterian Bx.3.41; Hyginus Poeticon astronomicon liber with woodcut illustrations of the constellations Sp Coll BD7-e.32 (Venice: 1485); Albumasar Introductorium in astronomiam with woodcut astrological illustrations Sp Coll BD7-e.16 (Augsburg: 1489)

Published by Ratdolt, Maler & Löslein: Appian Libri historiae Romanae Sp Coll BD7-d.16 (Venice: 1477)

Copies of Ratdolt's works, published by Franz Renner of Heilbronn, all bound together in Sp Coll Bk5-g.22: Pomponius Mela Cosmographia (Venice: 1478); Dionysius De situ orbis (Venice: 1478); J. de Sacro Bosco Sphera mundi & Gerardus Cremonensis Theorica planetarum (Venice: 1478)


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Julie Coleman August 1999