Astronomical clocks 1735-1796

This page provides my synthesis on the astronomical clocks described in Ludwig Oechslin’s Astronomische Uhren und Welt-Modelle der Priestermechaniker im 18. Jahrhundert, published in 1996. In the introduction to the chapter on 19th and 20th century astronomical clocks in the recent ``General history of horology'' (Oxford University Press, 2022), I wrote that in the 18th century, a number of remarkable astronomical clocks were made in Europe by Bernardo Facini (1665-1731), Johannes Klein (1684-1762), Johann Georg Neßtfell (1694-1762), Claude-Siméon Passemant (1702-69), Francesco Borghesi (1723-1802), David Ruetschmann (David a Sancto Cajetano, 1726-96), Michael Fras (Aurelius a San Daniele, 1728-82), Philipp Matthäus Hahn (1739-90), and many lesser figures, and this was a way to fill a gap, because in that general work, we unfortunately skipped the 17th and 18th centuries astronomical clocks.

At the time of publication, I was aware of all these clocks, and had seen several of them. I had also published an analysis of one of Passemant's clocks. But I had not been working in depth on most of the clocks I mentioned. The present work gives me an opportunity to have a closer look at these great clocks, those that Klaus Maurice called ``Die Uhrwerke der Theologe'' using Ludwig Oechslin's work on the ``Priestermechaniker'' as a basis.

Complete work

• Complete work in one volume

Note that for copyright reasons some images are not reproduced. They might be reproduced in the future.

Separate chapters

Since the chapters of the book are mostly independent, I have also split the book in the following 32 parts. The introduction contains important information that should be read first, but then the chapters can be read in any order, although I suggest to read those of each constructor in chronological order.

• Title
• Preface, table of contents and introduction
• Adams’ orrery in Munich
• Pater Aurelius’s clock in Munich
• Frater David’s clocks:
  • Frater David’s first clock in Vienna
  • Frater David’s Schwarzenberg clock
• Frater Fridericus’s mechanism in Bamberg
• Hahn’s clocks:
  • Hahn’s Weltmaschine in Stuttgart (Ludwigsburg's machine)
  • Hahn’s globe clock in Stuttgart
  • Hahn’s orrery in Furtwangen
  • Hahn’s astronomical clock in Basel
  • Hahn’s globe clock in Aschaffenburg
  • Hahn’s globe clock in Villingen
  • Hahn’s Weltmaschine in Gotha
  • Hahn’s tellurium in Winterthur
  • Hahn’s globe clock in Darmstadt
  • Hahn’s globe clock in Karlsruhe
  • Hahn’s globe clock in Zurich
  • Hahn’s Weltmaschine in Nuremberg
• Johann’s globe clock in Mainz
• Klein's clocks:
  • Klein’s geographic clock in Prague
  • Klein’s geographic clock in Dresden
  • Klein’s Tychonic clock in Prague
  • Klein’s Copernican clock in Prague
• Neßtfell's machines:
  • Neßtfell’s Planetenmaschine in Vienna
  • Neßtfell’s Planetenmaschine in Munich
• Rinderle’s clock in Furtwangen
• Seige's machines:
  • Seige’s metal orrery fragment in Prague
  • Seige’s wood orrery fragment in Prague
  • Seige’s Weltmaschine in Prague
• Stuart’s clock in Salzburg
• Conclusion and bibliography

Two caveats:

• This is a companion work

  As the title of the work implies, this is a companion work to Ludwig Oechslin's work. My book is basically unreadable without Oechslin's book at hand, and I strongly suggest to buy or borough it in order to follow my derivations. (And I am not getting any percentage!) Moreover, any person seriously interested in astronomical clocks should own Oechslin's book and read it.

• This is a work in progress

  I also want to stress that my work is a work in progress. I have basically only given the exact rational values of the astronomical periods of each clock and mechanism, I have tried to explain Oechslin's work, but I have not expanded much on other features of the clocks, nor on the historical details, although I have given the main bibliographical references and short bios. The chapters are also lacking detailed drawings of the gear trains, as well as photographs of the clocks and gears, except in a few cases. Some of these things may be added in future versions of my book.

Finally, it should be clear that no permission is given to store my work online anywhere, and this does in particular apply to the Chronospédia and Watch Library projects. No permission is given to index my work on these sites, for reasons I have explained elsewhere.

Denis Roegel, August 2025.