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Vacheron Constantin - The patented tropical gear train

Vacheron Constantin The patented tropical gear train

A new invention by Vacheron Constantin forms the backbone of two new astronomical complications.

The two different interpretations on the astronomical theme presented by Vacheron Constantin at the SIHH 2017 could not be further removed from each other. On the one hand is the Celestia Astronomical Grand Complication 3600 – a functional astronomical instrument; on the other is a selection of three Copernicus Celestial Spheres models showing off the artistic crafts with a more poetic interpretation of the astronomical theme. Yet both are based on a brand-new development by Vacheron Constantin that allows the tropical year (broadly speaking, the time it takes the Earth to complete one full orbit around the sun) to be calculated and displayed such that a one-day correction is required just once in 8,000 years!

Vacheron Constantin Calibre 3600 

In the Celestia Astronomical Grand Complication, this tropical gear train is used to display the running equation of time. Equation of time displays are already very rare in wristwatches, but running equation of time wristwatches are even rarer. Most equation of time watches display the difference between mean solar time (a 24-hour day) and sidereal, or civil, time (where a day is precisely 23 hours, 56 minutes and 4 seconds long) in the form of a scale that indicates whether solar time is ahead of or behind sidereal time, from -14 to +16 minutes. Or rather, the scale indicates a difference but it is not necessarily immediately apparent whether it is converting from civil to solar time or the other way around. The running equation of time solves this inconvenience by displaying the two times using two different minute hands. In the case of the Celestia Astronomical Grand Complication, the equation of time is visible in an instant by the gap between the “normal” minute hand and the solar time minute hand, which has an image of the sun at its tip. 

 Most equation of time watches, including Blancpain’s patented equation of time movement, rely on a bean-shaped cam to account for the elliptical orbit of the Earth. Vacheron Constantin has instead developed a totally new type of “tropical” gear train, which can display the exact time the Earth takes to orbit the Sun, specifically 365.2421898 days. In the case of the Celestia Astronomical Grand Complication, this gear train is responsible for the running equation of time. In the artistic Copernicus Celestial Spheres models it displays in real time the Earth’s current position on the trajectory of its orbit around the sun. At the same time, the ornately decorated Earth also revolves about its own axis in the 24 hours that correspond to a mean solar day. 

 Vacheron Constantin Copernicus Celestial Spheres

The contrast between the Celestia Astronomical Grand Complication (which, incidentally, contains the most complications that Vacheron Constantin has ever packed into a wristwatch) and the Copernicus Celestial Spheres models could not be greater. The former is clearly designed as an instrument and, given the wealth of information on display, is amazingly easy to read. The latter series of three models offers a canvas for depicting mankind’s relationship with the cosmos using the finest in hand decoration: from grand feu enamel to hand engraving and even a combination of traditional crafts and futuristic technologies with a hand-painted dial with laser-engraved and hand-painted sapphire crystal, laser engraved and hand-painted luminescent constellations and a hand-engraved Earth. In just three models, the 260-year old watchmaking firm covers a multitude of techniques and appeals to a variety of tastes at the same time. 


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An exploration of the history of Vacheron Constantin is a voyage of discovery, revealing the excellence of age-old watchmaking. Each timepiece is the result of the creative inspiration of the watchmaker or craftsman, dedicating their knowhow to the birth of outstanding watches. The Manufacture also works within a social and environmental code of ethics, and has had Responsible Jewellery Council certification since 2012.

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