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Ptolemy's Course of the Planets displayed by CLockwork

Ptolemy’s Course of the Planets Displayed by Clockwork

A Masterwork of Astronomy and Technology of the Renaissance created by Eberhard Baldewein 1563-1568

An extended Bookreview and Synopsis by Fortunat Mueller-Maerki (Sussex, NJ, USA)


Die Planetenlaufuhr –Ein Meisterwek der Astronomie und Technik der Renaissance geschaffen von Eberhard Baldewein 1563-1568. By Emanuel Poulle, Helmut Sändig, Joachim Schardin & Lothar Hasselmeyer. Published 2008 as ‘Jahresschrift 2008 – Band 47’ of the Deutsche Gesellschaft für Chronometie, Nurnberg, Germany. ISBN 978-3-89870-548-6. Hardcover, 272 pages. With a Welcome by Peter Plaßmeyer, an Explanation by Lothar Hasselmeyer, and an Introduction by Emanuel Poulle, 15 Chapters, Appendix, Bibliography, extensive Endnotes, and Image Credits. Illustrated with 11 full-page color plates, and 255 figures (mostly color photographs) in the text. Availabe for Euro 40, plus postage, from Deutsche Gesellschaft für Chronometrie, Gewerbemuseumsplatz 2, D90403 Nurnberg (Germany) (Website:www.dg-chrono.de ).

 Fig. 1:  The ‘Dresden Planetenlaufuhr’ by Eberhard Baldewein, made around 1565 for Duke August of Saxony.  Mars/Astrolabe side, with small timedial (minute hand and day of week disc). © 2008 Mathematisch-Physikalischer Salon, Staatliche Kunstsammlungen Dresden (Foto: Klut/Estel), Used in this article with permission of the copyright owner.  It may not be further reproduced, and the copyright for all pictures remains with the museum in Dresden Fig. 1: The ‘Dresden Planetenlaufuhr’ by Eberhard Baldewein, made around 1565 for Duke August of Saxony. Mars/Astrolabe side, with small timedial (minute hand and day of week disc). © 2008 Mathematisch-Physikalischer Salon, Staatliche Kunstsammlungen Dresden (Foto: Klut/Estel), Used in this article with permission of the copyright owner. It may not be further reproduced, and the copyright for all pictures remains with the museum in Dresden


Clocks featuring planetary displays, i.e. showing the position of the planets in real time, have always been among the most coveted timepieces, both for their use as scientific demonstration pieces, and as showpieces of ultra-complex mechanics. Even today, accurate orreries are difficult enough to design and build; but in the era before Copernicus’ heliocentric model of the solar system was accepted the difficulties were greater by orders of magnitude. The apparent retrograde movement of the planets (following the then accepted astronomic theory of Ptolemy with its epicyles) is difficult to represent in a mechanical model.


The most widely known mechanism of this kind undoubtedly is the ‘Astrarium’ which Giovanni de Dondi of Padua (Italy) built in the 1350s. Although that artifact was lost around 1530, copies of the illustrated, detailed construction notes recorded by the creator survive to the present. Several replicas were built in the second half of the 20th century and now serve as focal points of the early horology sections of a handful of prominent museums, including the newest design by Hank Gipmanns, to be unveiled in August 2009 at the Carillionmuseum in Asten, the Netherlands. Dondi’s notes were transcribed, translated and published in several different languages. The 1974 edition by Baillie, Lloyd and Ward, published by the Antiquarian Horological Society as Monograph No. 9 is probably the most widely known English language publication discussing such geo-centric planetary clocks.


While Dondi’s ‘Astrarium’ was probably the first clockwork-driven mechanical model of the motion of the planets according to the theory of Ptolemy, it certainly was not the only one, and it was designed to show the principle, rather than to model the epicyclical motion on a ongoing basis in real time. In other words: it was not much of a timekeeper. In the 1400s and throughout the 1500s certainly a number of them were built; there exists reliable documentary evidence on about 10 of them. It appears that only five planetary clocks in the Polemic tradition have survived to the present. (The sixth one, the public planetary clock by Giovan-Paolo Rainieri in the Piazza San Marco in Venice, has been so much modified that it has virtually lost its original planetary functions). Two of the five (the Philipp Immser (Strasburg) clock of 1557, now at the Technical Museum in Vienna, and the Georg Kostenbader (Strasburg), clock of 1588, now at the Gaasbeek Castle near Brussels, the latter now missing part of its internal gearing) hide the nature of the epicyclical motion behind the dial. The three others are based on the tradition of the unmechanized planetary position calculators based on the ‘epicycle on deferent’ theory of Campanus of Novarra, as published in 1260.


Of these three the French example by Oronce Fine, Paris, 1533 (possibly based on the work of Regomontanus in Nurnberg, today in the St.Geneviève Library in Paris) is the oldest one. The two others were designed by Eberhard Baldewein, the genius mechanic at the court of Wilhelm IV in Kassel (Germany) in the mid 16th-century, and built with the help of clockmaker Hans Bucher, while the cases are mainly the creations of master goldsmith Hermann Diepel. The earlier (and smaller) one - known as the ‘Willhelmsuhr’ - was conceived by Wilhelm IV of Kassel himself in the 1550s, while his astronomer Andreas Schöner provided the astronomical calculations. It is still in Kassel, still at the historic observatory at the Orangerie.


The second Baldewein astronomical clock – the subject of the book under review (see Figure 1) – was also built by the same craftsmen in Kassel and Marburg, but it was created for the court in Dresden, specifically for Count Elector August I of Saxonia. That clock, significantly larger, much more opulent, and mechanically more refined, is known as the ‘Dresden Planetenlaufuhr’ [Dresden Planetary Clock] and it also remains to this day in the building it has been in since the 16th century, the “Mathematisch-Physikalischer Salon” in the Zwinger in Dresden. (If you want to see it you have to wait till 2010 as the Museum is currently closed for renovations). That clock is unquestionably the pinnacle of planetary clocks based on the theory of Ptolemy.


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Comments on the Book:

There is no question in my mind that the artifact described in this book is one of the most important timepieces in the history of horology, if not in the history of mechanics. There is little doubt that – at the time of its construction - this machine was the most complex geared apparatus ever constructed in the history of mankind. To have a ‘superstar’ as the subject of a book alone does not automatically assure that the book under review is a great or even an important book. But this reviewer believes that this book is a highly important book because the skills and qualifications of its creators, and the extreme care, the unending work and thoughtfulness that went into producing the book, are commensurate with the quality of the artifact. The fact that four extremely skilled people from very different disciplines (a mechanical engineer, an astronomer, an art historian and a museum curator) converged in one time period with the burning desire to fully document the same object is a rare coincidence. And this chance constellation produced an extraordinary book. A publication of this complexity is bound to include some glitches, but I have found only one minor error (the legend of the schematic of the quarter train misidentifies the count wheels in Bild 6-1).

It would be unfair to hold it against the title that this book has appeared ‘only’ in a German language edition – and the likelihood of it ever being fully translated into an other language unfortunately is miniscule. Undoubtedly, an English language book would have been easier to understand for more readers globally; but the Baldewein clock, while being of wide interest as a part of human culture, is primarily a core element of Germany’s cultural heritage, and thus deserves to be documented primarily in German. The clock can also bee seen as a symbol of the cultural and political upheavals of its time, of reformation vs. counter-reformation, astronomy vs. astrology, Catholicism vs. Protestantism, the ‘saving the phenomena’ science vs. observational science, etc. In spite of all these complexities the publishing team at DGC deserves credit for creating a book that is relatively easy to follow – and useful – even for readers whose primary language is not German. Admittedly, the casual foreign reader will not understand much, but the most likely foreign reader, either somebody deeply either interested in Ptolemy’s planetary model, or someone already quite familiar with complicated renaissance timekeepers, is likely to not only understand quite a bit of the content, but also to enjoy the reading. Having more than 250 superb photographic images and very clear schematics spread throughout the text is an immense help for the foreign reader. Even if you cannot read a word of German the pictures alone make the book worth buying if you have any interest in the subject matter.

If you do read German the text of the book is delightfully easy to read considering the sometimes highly technical and extremely complex subject matter. It provides a glimpse into the time it was created, an appreciation for the geniuses who have thought it up and built it. Reading the book evokes gratitude for the person who commissioned the clock, and the many custodians who have helped it survive to the present. I am deeply grateful to the authors for having created the book, and in awe of the countless people who - over the decades - have not given up in spite of overwhelming odds against them and have persevered in getting the story of the Baldewein clock into print more than 400 years after it was created. Thank you to the authors, to the Mathematisch Physikalischer Salon at the Dresden Museum, to the DGC and all others involved.

Acknowledgements: Given his lack of astronomical knowledge the reviewer is much indebted to Dr. Eberhard Zelinsky for helping me better understanding Ptolemy’s theory and the historic/political context of the clock, and to Dieter Tondock of DGC and Lothar Hasselmeyer of the Mathematisch-Physikalischer Salon for securing the reproduction rights of the images accompanying this review. All the photographs are © 2008 Mathematisch-Physikalischer Salon, Staatliche Kunstsammlungen Dresden (Foto: Klut/Estel), and the schematics are © 2008 Lothar Hasselmeyer. They may not be further reproduced, and the copyright for all pictures remains with the museum in Dresden.

Fortunat Mueller-Maerki, Sussex NJ
August 2009


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