An ultra-thin calibre (less than 8 MM thick) houses 19 complications for a double-sided minute repeater that displays solar, sidereal, and solar time with an additional perpetual calendar.

The tangible and the conceptual come together to inspire the imagination and express dreams with real-life applications for counting hours and observing the heavens above. A wristwatch that shows off the esthetic and technical prowess of Les Cabinotiers, the pink gold Astronomical Striking Grand Complication, is precisely the type of magical thinking that watch enthusiasts dream of.

Building upon an ultra-thin movement with a minute repeater mechanism, Vacheron Constantin reworked their Manufacture 1731 calibre to accommodate the additional astronomical complications to create the new 1731 M820 calibre. Equipped with a total of 19 complications, the movement is still barely 7.84 MM thick. Now, with all this technical mastery going on behind the curtain, here is Vacheron Constantin enchantment revealed:

Let’s start with the front. The central hands indicate the hours and minutes, as well as solar time. Solar time, quite simply, can be described in layman’s terms as “sundial” time. Lining up with traditional hours four times per year, this enables watchmakers to program this foreseen event mechanically, as indicated beautifully by the third central hand with the serrated sun.

The subdial at three illustrates the date with a serpentine hand, the days, months, and leap years of the perpetual calendar appear in small windows between twelve and two. Complimenting the perpetual calendar is the date and moon phase indicator at nine, also signifying day and night. On the lower half of the dial, the pointer displays at six tell us the time of sunrise and sunset, with a vertical central linear window revealing the length of day and night. For celestial dreamers, the aperture at four shows us the signs of the zodiac, seasons, solstices, and equinoxes.

Got all that? Now here comes the mindblowing part. The reverse side, with its dazzling celestial sky chart, indicates the highly ethereal sidereal time.

Despite the volume of complications residing in this watch, it remains an ultra-thin caliber with a sub-8mm waistline
Despite the volume of complications residing in this watch, it remains an ultra-thin caliber with a sub-8mm waistline

A rare complication that separates the professionals from the amateurs, sidereal time, similar to solar time that uses the angle of the sun, sidereal time follows the stars. According to the National Institute of Standards and Technology, sidereal time is a “time scale that is based on Earth’s rate of rotation measured relative to the fixed stars.” On the Astronomical Striking Grand Complication – Ode to Music according to the press materials, “the lower disc shows a sidereal time scale punctuated by the cardinal points, which thus rotates in step with sidereal time.” Magical, to say the least.

If you look closely, a second disc reveals a white ellipse representing the celestial equator and a red ellipse for the ecliptic (our sun’s path during the year). The first is a “projection” of the Earth’s equator into the celestial sphere. At the same time, the red ellipse represents “from a heliocentric point of view — the plane of the Earth’s orbit serving as a reference to celestial coordinates.” The movable lower disc will accelerate by approximately four minutes per day in relation to the outer disc, as to indicate the current month at exactly midnight by a small yellow arrow. Slightly easier to understand, the outer blue ring shows the months of the year. Whew.

The display of the Les Cabinotiers Astronomical Striking Grand Complication is incredibly easy to read, despite its complexity
The display of the Les Cabinotiers Astronomical Striking Grand Complication is incredibly easy to read, despite its complexity

Technical Specifications

Movement

Calibre 1731 M820, Mechanical manual-winding, 36 mm diameter, 7.84 mm thick, 600 components, 36 jewels, 3 Hz (21,600 vibrations/hour) Hallmark of Geneva certified timepiece. Approximately sixty hours of power reserve. Developed and manufactured by Vacheron Constantin.

Case

45 MM in 18K 5N pink gold. 12.54 MM thick. “Piece Unique” and “Les Cabinotiers” inscriptions engraved between the lugs of the timepiece.

Dial

Blue opaline with 18K pink gold applied baton-shaped hours markers.

Strap

Brown Mississippiensis alligator leather strap with alligator leather inner shell, hand-stitched, saddle-finish, large square scales with an 18K 5N pink gold folding clasp delivered with an additional 18K 5N pink gold buckle polished half Maltese cross-shaped buckle.