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The Encyclopedia of Horology

Complication · Calendar & astronomy

Tellurium

Partially verified

A complication showing the relative positions and motions of the Earth, Sun, and Moon.

Definition

A complication showing the relative positions and motions of the Earth, Sun, and Moon.

Historical origin

Based on the three-dimensional astronomical models used for education.

How it works

A miniature Earth rotates on its axis while orbiting a central Sun, with the Moon orbiting the Earth.

Requires extremely complex differential gearing to maintain the relative speeds.

Pocket watch context

Exceedingly rare; usually found in large clocks.

Wristwatch context

A high-art complication in wristwatches from makers like Ulysse Nardin.

Identification

  • Three-dimensional globes or rotating discs representing the Earth-Moon-Sun system

Servicing notes

Ultra-complex; requires factory-specialist service.

General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.

Diagram

date ring, thirty-one positionsdate aperturedriving wheel and jumper
Schematic: calendar work under the dial. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Sources & references

  1. de Carle, D., Watch and Clock Encyclopedia
  2. Britten, F. J., Old Clocks and Watches and Their Makers
  3. Horological Journal (British Horological Institute), technical articles

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