Vacheron Constantin: Les Cabinotiers Celestia Astronomical Grand Complication Homage to Ptolemy & Copernicus

Vacheron Constantin celebrates its 270th anniversary and its quest for excellence with a new series of Les Cabinotiers watches entitled ‘La Quête’, which pays tribute to astronomy and the odysseys of ancient times. Representing significant technical and aesthetic challenges, these watches highlight Vacheron Constantin’s expertise in creating grand complication watches enhanced by the decorative crafts. The Celestia Astronomical Grand Complication – Homage to Ptolemy and – Homage to Copernicus, are powered by the Manufacture movement Calibre 3600, first presented in 2017 in the Les Cabinotiers Celestia watch. Five years in development, the movement comprises 514 finely adjusted and meticulously decorated components and incorporates 23 astronomical complications. The double-sided calibre represents not only a significant technical achievement but also, with a thickness of only 8.7 mm, a notable feat of miniaturisation. 

TRIBUTE TO TWO GREAT ASTRONOMERS

The observation of the stars, the cycle of seasons and the alternation of day and night have always aroused human curiosity and, from very early on, mankind has sought to model these rhythms. Thanks to the first astronomical observatories, space-time became a more concrete concept, as it could be explained in terms of measurable rhythms. Ptolemy, the 2nd-century astronomer from Alexandria, imagined a universe in which Earth remained motionless at the centre, with the stars and planets revolving around it in perfect harmony. Many centuries later, the Polish astronomer Nicolaus Copernicus identified the Sun as the centre, returning to the long-forgotten heliocentric theory first proposed by Aristarchus of Samos in the 3rd century BC, he overturned opinions that had prevailed for 1500 years and thus paved the way for a new interpretation of the sky. 

The case of each watch expresses a different vision of the cosmos, engraved with an illustration of the movement of the planets according to their respective systems: that of Ptolemy, placing the Earth at the centre of the universe, and that of Copernicus, symbolising the solar revolution that gave rise to modern astronomy. 

THREE DISTINCT HOURS

The Celestia Astronomical Grand Complication watch is distinguished by its display of three times – civil, solar and astral – each driven by its own gear train. Civil time and solar time are indicated by central openworked hands on the front dial. Due to Earth’s elliptical orbit around the Sun and the 24° inclination of its axis, the time that elapses between two passages of the Sun at its zenith differs slightly each day throughout the year. This difference between the solar (true) day and the 24-hour civil (mean) day, known as the equation of time, ranges from -16 to +14 minutes depending on the time of year and coincides only four times annually, at the solstices and equinoxes. As these variations are identical from one year to the next, they can be programmed mechanically using a cam that controls the display of the time differential. An added complexity of this calibre is that the differential is represented as a running equation of time, in which solar time is indicated by a minute hand tipped with a ‘sun’ that is coaxial with the hands that display civil time. This hand enables an instantaneous reading of both times, as it moves ahead of or behind the mean-time hand as the year progresses. 

Sidereal time is shown on the back of the watch by means of a celestial map formed by two superimposed sapphire discs – a fixed upper disc marked with the constellations and a mobile lower disc. As Earth rotates on its axis and revolves around the Sun, the time it takes to complete a full 360° rotation relative to a fixed star in the sky is approximately four minutes less than a calendar day. Known as a sidereal day, its duration is exactly 23 hours, 56 minutes and 4 seconds. The sidereal time scale is marked around the edge of the mobile lower disc, which rotates four minutes faster than civil time each day and the current date is indicated by a triangular yellow pointer. 

On this rotating disc, an off-centre blue ellipse serves as a background sky, indicating which of the constellations marked on the upper disc are visible from a given location on Earth in real time – a constantly changing astral ballet. A white elliptical line indicates the celestial equator (a projection of Earth’s equator inclined at 24°) and a red elliptical line indicates the ecliptic (the plane of Earth’s orbit). 

ASTRONOMICAL MASTERY

As well as civil time and the equation of time, the front dial displays seven additional complications, arranged on a grained background of 18K white or pink gold, depending on the model. A perpetual calendardisplays the days and months in windows at 1 o’clock, and leap years in a small circular window set above a counter at 3 o’clock on which the date is indicated by a serpentine hand. This perpetual calendar, programmed until 2100 – a non-leap year – is complemented by a precision moon phase indicator. This function, which requires only one day’s correction every 122 years, is displayed at 9 o’clock by means of two superimposed discs, an upper, transparent disc bearing a laser-engraved representation of the moon and a lower disc shaded to indicate day and night. The age of the moon, or number of days since the last new moon, can be read around the edge. 

The lower part of the dial displays sunrise and sunset times, indicated by slender hands on graduated scales, as well as the length of day and night on a gauge between them. At 4 o’clock, a rotating annual disc bears the astronomical signs of the zodiac, the seasons, the solstices and equinoxes. At 11 o’clock, a mareoscope or tide gauge – a rare watchmaking complication – completes the ensemble of astronomical complications. Its display combines a tidal level indicator and a three-dimensional representation of the Earth-Moon-Sun alignment. This alignment precisely controls the amplitude of tides, which have the highest range when the three celestial bodies are on the same axis, namely at New Moon and Full Moon. 

On the reverse side of the watch, the display of sidereal time is complemented by a peripheral power reserve indicator, with a duration of three weeks ensured by six barrels mounted in series. Held by asymmetrical fixing bars, the one-minute tourbillon also appears on the back of the watch, a design decision made to leave sufficient space for the astronomical indications on the front. Counteracting the effects of Earth’s gravity by constantly shifting its position, the tourbillon cage takes the form of a Maltese cross, Vacheron Constantin’s emblem since 1880. 

TWO UNIQUE PIECES

Ptolemy’s geocentric system is illustrated by a hand engraving of the planets orbiting the Earth in the form of a planisphere surrounding the crown. The master engraver’s work began by drawing the ellipses corresponding to the planets’ trajectories using drypoint. As these ellipses extend onto the lugs and bezel, it was especially challenging to maintain symmetry and regularity of line to ensure that there are no visual breaks between the components of the case. This was followed by hollowing out the spaces between the ellipses using the champlevé engraving technique, to a depth of just 1/10th of a millimetre on the bezel and 2/10ths on the case and lugs. The hollowed areas were then finely hand-chased to create a ‘sandblasted’ appearance, creating a striking contrast with the polished ellipses on the surface. To accentuate the effect of depth, the planets are subtly domed and finely textured to reproduce their appearance in the cosmos and Earth, also in relief, features hand-polished continents. 

Illustrating Copernicus’ heliocentric theories, the crown symbolises the Sun radiating its rays onto the case and lugs, while the planets move through their respective orbits. The champlevé engraving technique, which involves chiselling the hollows and polishing the ridges, was also used on this piece, the design of which presented an additional challenge: the geometric centres of the planetary orbits, positioned on the left side of the case, are outside the frame of the case. This feature required the creation of a special tool to draw circular arcs with a compass, an exercise made all the more complex by the curved surface. The planets are engraved in relief to create a domed effect and polished to contrast with the texture of the chased background. 

Both Celestia Grand Astronomical Homage to Ptolemy & Copernicus timepieces come with a dark blue alligator strap and a gold deployant clasp. Created as one-of-a-kind pieces, they feature the engravings “Pièce Unique,” “Les Cabinotiers,” and the “AC” emblem on the caseback.