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The Encyclopedia of Horology

Astronomical clock with mechanical automata and perpetual calendar work · France (Strasbourg Cathedral)

Strasbourg Astronomical Clock

Verified

The present clock is the third built at Strasbourg Cathedral; Schwilgué incorporated a mechanical computer capable of calculating moveable feasts (including Easter) and functioning correctly through the Gregorian calendar's leap-year exceptions.

Technical facts

Calendar computation
Mechanical computus mechanism for moveable feasts, accounting for the Gregorian leap-year rule
Automata
Procession of the Apostles and a mechanical rooster that crows at noon
Astronomical display
Orrery-style display of planetary positions known at the time of construction

Historical significance

  • The present clock is the third built at Strasbourg Cathedral; Schwilgué incorporated a mechanical computer capable of calculating moveable feasts (including Easter) and functioning correctly through the Gregorian calendar's leap-year exceptions.
  • A celebrated example of pre-electronic mechanical computation applied to calendar astronomy, distinct from being merely a large decorative clock.
  • Because three successive clocks have occupied the site, researchers should always specify which clock (1354, 1574 or 1842) a given claim or fact refers to.

Background

The third Strasbourg astronomical clock was designed and constructed by Jean-Baptiste Schwilgué between 1838 and 1843. Before beginning the physical construction, he spent a full year preparing a team of thirty workers for the complex task. The clock was officially inaugurated on the final day of 1842 and stands within the Cathédrale Notre-Dame of Strasbourg. This mechanism was designed to replace outdated systems with state-of-the-art technology, featuring a perpetual mechanical Gregorian computus devised by Schwilgué in 1816.

Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.

Construction and mechanism

  • The clock displays mean solar time with gold hands and Central European Time with silver hands.
  • Its functions include a planetary calendar that tracks the positions of the Sun and the Moon.

Later history

  • A 1:5 scale working model of this third clock was constructed in 1887 by a Sydney watchmaker named Richard Smith.
  • The model created by Richard Smith is currently held in the collection of the Powerhouse Museum in Sydney, Australia.
  • In the 1970s, Frédéric Klinghammer built a reduced replica of the clock's computus mechanism.

Where sources differ

  • Date. This record gives: “Current mechanism completed 1842”. The cited history dates construction to 1838–1843, with the clock inaugurated on the last day of 1842.

Photographs

Strasbourg Astronomical Clock (museum replica)
Strasbourg Astronomical Clock (museum replica) — Museumsfotografierer, Public domain. Wikimedia Commons file page
Strasbourg Astronomical clock Equations
Strasbourg Astronomical clock Equations — Tangopaso, Public domain. Wikimedia Commons file page
Strasbourg Cathedral Astronomical Clock - Diliff
Strasbourg Cathedral Astronomical Clock - Diliff — Diliff, CC BY-SA 3.0. Wikimedia Commons file page
How to Visit Strasbourg Astronomical Clock, the Alsace | solosophie
How to Visit Strasbourg Astronomical Clock, the Alsace | solosophie — solosophie.com, Rights unverified — web image search result, review pending. Web page (solosophie.com)
Rochelimit's Symbology of Astronomy: Strasbourg Astronomical Clock
Rochelimit's Symbology of Astronomy: Strasbourg Astronomical Clock — Commons, Rights pending — source and visual checks completed; permission not yet requested. Web page (symbology-astronomy.blogspot.com)

Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.

Sources & references

  1. Strasbourg astronomical clock, Wikipedia (English), retrieved 2026-10-28 (text CC BY-SA 4.0)
  2. Strasbourg Cathedral, published horloge astronomique visitor materials
  3. Antiquarian Horological Society, comparative articles on astronomical clocks

Where sources disagree, the disagreement is stated rather than resolved silently.