The calendar and astronomical functions play a starring role on both sides of the watch. On the front, where the mechanical ballet of the tourbillon can be admired at 6 o’clock, the perpetual calendar indications are displayed on three counters. Positioned in the upper part of the dial, they respectively show the date, day and month. Designed to keep track of the Gregorian calendar’s vagaries without any need for adjustment until 2100, this horological complication is further enhanced by the indication of the leap-year cycle. The latter appears in a small aperture next to the hand indicating the torque of the minute repeater mechanism between 1 and 2 o’clock. This striking mechanism power reserve is matched by an indication of the movement power reserve, which can be read by means of a serpentine pointer coaxial with the day of the week hand.
The complex mechanics of this piece also provide an astronomical reading of time representing a tribute to Johannes Kepler (1571-1630), regarded as one of the founders of modern astronomy for having discovered the laws of planetary motion, in perfect agreement with Copernicus’ heliocentric hypotheses. The first astronomical functions thus appear on this same opaline champagne-coloured dial, starting with the equation of time positioned between 10 and 11 o’clock. As the Earth’s path around the Sun is not circular but elliptical, and since the Earth’s axis is inclined at 24° to the plane of its orbit, the time between two zenith passages of the Sun is not the same throughout the year. This difference between the (true) solar day and the (average) 24-hour civil day ranges from -16 to +14 minutes depending on the time of year and coincides only four times a year. Called the equation of time, or time correction in astronomical language, this differential is displayed by a dedicated pointer, while sunrise and sunset times – adjusted according to a reference city – appear at the bottom of the dial.
An astronomical watch as conceived by the watchmakers at Vacheron Constantin would not be complete without a sidereal time indication. This display finds its place the back of the watch in the shape of a rotating disc depicting the celestial vault with its constellations observable from the Northern hemisphere. Taking a fixed star in the sky as a reference point, the time required for the Earth to complete a full 360° rotation, or sidereal day, is exactly 23 hours, 56 minutes and 4 seconds. Since the Earth is both spinning on its axis and revolving around the Sun, it takes about four minutes less than a calendar day to return to its point of origin relative to a given star. On this model, the "celestial" disc thus performs a complete rotation according to sidereal time with the time displayed on the periphery, opposite the date appearing on the periphery of the mobile disc. This same date is read off by a large central hand moving over the fixed outer flange bearing a scale graduated in five-day increments. This hand also indicates the sign of the zodiac, the season and the four dates corresponding to the solstices and equinoxes. Finally, the small central hand indicates the age of the moon, i.e. the number of days that have elapsed since the last full moon.
Comprising 839 parts and measuring a total 33.90 mm in diameter and 12.15 mm thick, this movement endowed with a 58-hour power reserve represents a technical feat that is all the rarer in that it displays all its functions in a perfectly legible manner on both sides. Equipped with a balance oscillating at a rate of 18,000 vibrations per hour (2.5 Hz), it is housed in a 47 mm-diameter 18K 5N pink gold case, of which the characteristics been specifically designed to provide the best possible sound quality for the minute repeater.
Each year, the Les Cabinotiers department unveils a range of single-piece editions relating to a theme cherished by Vacheron Constantin. The year 2021 was dedicated to “Le Temps Céleste”
(which means Celestial Time), with timepieces referring to the astronomical origins of time measurement.
From the dawn of civilisations, the cycle of days and seasons, the evolution of constellations in the night sky, the phases of the moon and eclipses have exerted an almost mystical fascination. Eager to unravel the mysteries of the universe, the first human beings found in mythological tales a cosmogony blending legends with poetry. At a very early stage, the first scientific minds attempted to decipher the rhythms of Nature and to organise them according to predictable patterns.
It was from these calculations, and with the appearance of writing, that the first calendars were born, before the Babylonian sexagesimal system gave meaning to the physical division of time into units of angle. Traditional watchmaking is a direct heir to this rigorous and scientific approach, expressed today on watches with depictions of the calendar, the sky chart, moon phases, tides and seasons, and even civil, solar and sidereal time with their differentials. Vacheron Constantin has nevertheless sought to endow these genuine observation instruments with all the charm of the founding myths through the subtlety of its craftsmanship, through its work in guilloché engraving and the engraving of symbolic motifs, or in the “stellar”
glittering of gem-set stones. This new Les Cabinotiers range is the expression of exceptional expertise in astronomical watches, dedicated to the poetry of time.
Vacheron Constantin and astronomical watches
Astronomical watches enjoy a rich and longstanding tradition within the Maison. The Vacheron Constantin archives reveal a first perpetual calendar in 1884, integrated into a double-sided yellow gold pocket watch, now part of the Maison’s private collection. This was the beginning of a mechanical “epic”
that would singularly take shape at the turn of the century. In 1900, the Maison set up a workshop exclusively dedicated to the assembly of watches with complications, often incorporating astronomical functions. Orders flooded in for complicated and even very complicated watches. The perpetual calendar was then combined with other technical feats such as those enriching a 1905 pocket watch comprising a minute repeater, split-seconds chronograph and perpetual calendar with phases and age of the moon.
Delivered in 1929, the pocket watch made for King Fouad I of Egypt with chronograph, perpetual calendar, Grande and Petite Sonnerie and minute repeater functions is characteristic of this golden age. This exceptional watchmaking expertise, later applied to wristwatches, would be powerfully expressed in the Tour de l’Île with its 16 horological and astronomical complications, produced in 2005 to mark the 250th
anniversary of the Maison. It features a sky chart, a complication that has become a speciality of Vacheron Constantin. Reference 57260, which has 57 complications, also features a sky chart, notably accompanied by sidereal time and a secular Hebrew calendar. In 2017, Vacheron Constantin once again innovated with Calibre 3600, powering displays of civil, solar and sidereal time, the latter synchronised with a mobile representation of constellations.
In the Vacheron Constantin universe, Les Cabinotiers represents a department in its own right dedicated to the personalisation of Grand Complication models and single-piece editions. This tradition dates back to the 18th
century, an age when master-watchmakers were called cabinotiers and worked in ateliers bathed in natural light, known as cabinets and located on the top floors of Geneva’s buildings. In the hands of these learned artisans, open to the new ideas of the Enlightenment, exceptional timepieces were born, inspired by astronomy, mechanical engineering and the arts. This expertise, which constitutes the great Geneva watchmaking tradition, has been flowing through Vacheron Constantin’s veins since 1755.