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SIHH 2017: Vacheron Constantin - Les Cabinotiers Celestia

The latest, exceptional grand complication watch from Vacheron Constantin is a piece unique which combines astronomy and watchmaking art, the Celestia Astronomical Grand Complication 3600.

The result of five years of development and the full time work of one dedicated master-watchmaker, this new masterpiece displays twenty-three essentially astronomical complications on the front and back dials, providing a reading of time in three modes – civil, solar and sidereal – each driven by its own gear train.

It is another demonstration of the technical expertise cultivated by the Maison in the field of astronomical complications. This expertise dates back to the late 19th century, with pocket-watches featuring a perpetual calendar, moon phases and sidereal time; and later, in 1914, equipped with a running equation of time display. More recent exceptional models – such as the Tour de l’Île (16 complications) presented in 2005 and Reference 57260 (the world’s most complicated watch, 57 complications) in 2015 – represented true milestones in the history of mechanical horology.

The timepiece functions notably feature the triple-time civil, solar and sidereal displays powered by three distinct gear trains, including a "tropical" gear train dedicated to all the solar functions.

  • Civil time is a universally recognised mean time based on the fictional principle that the Sun moves around the equator at a constant speed throughout the year, averaging one full turn every 24 hours. This convenient and conventional choice divides the year into 365.25 days, each day into 24 hours and each hour into 60 minutes.
  • True solar time is based on the visible trajectory of the Sun in the course of the day, expressed through its hour angle measured at a given place and time. Depending on the day of the year, the difference between solar time and mean time ranges from +14 to -16 minutes, with the two exactly coinciding only four times a year. This discrepancy is due to the fact that the Earth’s orbit is elliptical (and not round); that the Sun is not in the centre of this ellipse; that the Earth does not follow this orbit at a constant speed; and lastly that the Earth’s rotation axis is tilted in relation to the plane of its orbit.
  • Sidereal time is an astronomical time scale based on the Earth’s rate of rotation measured with respect to the apparent motion of the ‘fixed’ stars as observed from a local meridian, sidereal time differs from mean time by approximately four minutes per day, meaning that 24 sidereal hours correspond to 23 hours, 56 minutes and 4 seconds of civil time. 

Swept over by a pair of white gold open-tipped hands, civil (or standard) time is read off in the traditional manner on the front dial.

To measure and display the difference between civil and solar time, this timepiece is equipped with a complex and refined equation of time mechanism. Moreover, the latter is also a ‘running’ equation of time, a kind rarely seen in wristwatches and indicating solar time by means of an additional coaxial pink gold minutes hand adorned with a cut-out sun.

The equation of time is generally displayed by a hand moving across an auxiliary sector with a scale running from +14 to -16 minutes and requiring a bit of mental arithmetic to check solar time. The running equation of time is far more complex to create and enables instant readings of solar and civil times. To ensure exactitude and precision, Vacheron Constantin has adjusted it to a tropical gear train simulating the tropical year, meaning the time the Earth takes to make a full turn around the Sun and corresponding to 365.2421898 days.

Thirdly, sidereal time is read off on the back of the watch.

Sidereal hours and minutes are indicated in an original and refined way by means of two superimposed sapphire discs. The lower one forming the background features the celestial dome, the celestial time minute-track and the four cardinal points; while the second one placed on top bears the constellations, the projections of the equator (white circle) and the ecliptic (red circle) – the latter depicting the Sun’s annual trajectory as seen from Earth. This Lambert projection is an authentic scientific map corresponding to the constellations in the Northern Hemisphere.

As well as readings of civil and solar time by the three coaxial hands, the front dial also features a perpetual calendar (day of the week, month and leap-year cycle) with a precision moon phase as well as a remarkable mareoscope composed of a tide level indicator and a 3D depiction of the Earth-Moon-Sun alignment. Tides are governed by physical laws and depend on the gravitational attraction and centrifugal forces of these three heavenly bodies.

These precious functions are complemented by sunrise and sunset times, pointed two by slim hands moving over two graduated scales, as well as the length of day and night appearing on a special gauge at 6 o’clock.

This set of complications that occur but rarely in the Fine Watchmaking sky is further enriched by other captivating indications arranged in a semi-circle: zodiacal signs, seasons, solstices and equinoxes. Solstices – at which the day is at minimum or maximum length – occur twice a year in summer and winter; whereas equinoxes – when day and night are of equal length – correspond to the start of spring and autumn.

On the back of the watch, the second dial is composed of two superimposed sapphire discs showing a translucent celestial chart for which a patent has been filed. In the foreground, this display depicts the constellation viewed from the Northern Hemisphere, ringed by an anthracite inner bezel ring showing the months of the year as well as a gauge-type power-reserve indicator. 

On this same transparent disc, two ellipses – one red and the other white – respectively correspond to the projections of the ecliptic and the celestial equator. Positioned beneath the constellation, a second disc rimmed by a graduated scale displays sidereal time and the four cardinal points, while an anthracite-coloured sphere reveals a see-through view of the celestial map. 

In addition, this detailed sky chart also provides a glimpse of the tourbillon at 6 o’clock.

Measuring a mere 8.7 mm thick, the 2.5Hz (18,000 vibrations/hour) manual-winding and fully integrated 514-part Calibre 3600 is equipped with six barrels, couple by three, to guarantee three full weeks of autonomy!

To achieve this incredible result, Vacheron Constantin worked simultaneously on two main fronts: by seeking to save energy on the one hand, and by increasing the size of its power supply. 

So as to optimise the energy stored as well as its transmission, the barrel springs are made from a sturdy and ductile Bioflex alloy, while the involute gears mesh in an ideal manner. Finally, the six barrels guarantee a substantial storage volume, while keeping the caliber as slim as possible. 

This unique mechanism, equipped with a tourbillon featuring a large balance wheel for enhanced precision and regularity, fits neatly inside an elegant 45 mm x 13.6 mm white gold case.

Like the entire Vacheron Constantin collection, Les Cabinotiers Celestia Astronomical Grand Complication 3600 bears the Hallmark of Geneva, confirming that it meets the numerous demanding criteria governing this prestigious quality certification. 

Issued in a limited edition of one, the Celestia is fitted with an alligator leather strap secured by a white gold pin buckle, it comes in a luxurious presentation box adorned with wood marquetry. The price is on request.

List of complications

Calendar and moon phase (mean time gear train)
1. Day by aperture
2. Date by hand
3. Month by aperture
4. Leap year by aperture
5. Perpetual calendar
6. Day/Night indication
7. Precision moon phase
8. Age of the moon

Solar functions (tropic gear train)
9. Equation of time
10. Running equation of time
11. Sunrise time
12. Sunset time
13. Length of day
14. Length of night
15. Seasons, solstices, equinoxes and zodiacal signs

16. Tide level indicator
17. Sun-Earth-Moon conjunction, opposition and quadrature

Celestial chart (dedicated sidereal gear train)
18. Celestial chart of the northern hemisphere with indication of the Milky Way, the ecliptic and
the celestial equator
19. Celestial time hours
20. Celestial time minutes

Further functions
21. Tourbillon
22. 3 weeks of power reserve (6 barrels)
23. Power reserve indication

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