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The Encyclopedia of Horology

Astronomical clock with calendar dial and mechanical figures · Czech Republic (Bohemia)

Prague Astronomical Clock (Orloj)

Partially verified

One of the oldest astronomical clocks in the world still operating, showing the position of the sun and moon against the zodiac in addition to time.

Technical facts

Astronomical dial
Shows time, sun and moon position against zodiac, using a Prague-specific (not modern) astronomical projection
Calendar dial
Added in the 15th century, with a 19th-century calendar-plate replacement by Josef Mánes
Figures
Mechanical apostles and allegorical figures animate on the hour

Historical significance

  • One of the oldest astronomical clocks in the world still operating, showing the position of the sun and moon against the zodiac in addition to time.
  • Has been damaged and rebuilt multiple times, notably after fire damage in 1945; the surviving mechanism is a mixture of medieval design intent and multi-century restoration and replacement work, which should be stated plainly rather than presenting it as untouched medieval fabric.
  • A long-associated legend about the clockmaker being blinded to prevent him building a rival clock is folklore, not documented history, and should not be repeated as fact.

Photographs

Czech-2013-Prague-Astronomical clock face
Czech-2013-Prague-Astronomical clock face — Godot13, CC BY-SA 4.0. Wikimedia Commons file page
Praha Astronomical Clock 01
Praha Astronomical Clock 01 — Uoaei1, CC BY-SA 4.0. Wikimedia Commons file page
Praha Astronomical Clock 02
Praha Astronomical Clock 02 — Uoaei1, CC BY-SA 4.0. Wikimedia Commons file page

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

Sources & references

  1. Prague City Tourism, official Orloj history published materials
  2. Antiquarian Horological Society, comparative articles on astronomical clocks

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