A highly technical, unique edition, the Vacheron Constantin Armillary Tourbillon Perpetual Calendar ‘Planetaria’ celebrates the quintessential astronomical function: the perpetual calendar with precise moonphase.

With sophisticated complications that lead to a unique aesthetic signature, the Vacheron Constantin Armillary Tourbillon Perpetual Calendar ‘Planetaria’ is equipped with a new extraordinarily complex 1991 Caliber manufacture movement. With 745 components, the manual caliber 1991 is the result of a four-year development process. The movement feeds two rotating globes that represent the Earth’s hemispheres, regulated by a double-axis armillary tourbillon. It corresponds to an innovative interpretation of the perpetual calendar, the astronomical complication par excellence that “reads” the specifics of the calendar without requiring adjustments until 2100. Another highlight is the retrograde indications of the days, date and months of the perpetual calendar. Mounted on spheres to ensure a linear and uniform operation, the date display follows a circular arc to the right of the hour and minute dial. According to the astronomical vocation of the watch, the center of the hour and minute display is dedicated to the moonphase. These appear according to their respective evolution in the two hemispheres, in perfect symmetry with the two rotating globes and with a degree of precision that requires a correction of one day every 122 years.

The perpetual calendar functions continue with the leap year to appear through an opening at 5h, together with circular indications of the day and month at 12h and 6h, based on a jumping retrograde display system. At the center of the two counters, the two globes that represent the northern and southern hemispheres perform full rotations in opposite directions on a 24-hour scale. The shaded areas of the domed sapphire crystal used for the day / night indication were positioned so that the armillary tourbillon resembles a sun casting its rays across the Earth’s surface. Making the ultra-thin sapphire crystal – 0.35 mm – with the domes and extending over the retrograde display of the date required a lot of ingenuity. A button integrated in the crown allows simultaneous adjustment of the World Time function in both globes.

The complex mechanics of the 1991 Caliber are perfectly synthesized in its Armillary tourbillon, a technical challenge, in addition to a spectacular view. This regulating device with a power reserve of 60 hours is positioned on the left side of the piece, below the sapphire crystal ‘bubble’. Forming a sphere in perpetual motion, the tourbillon was named “Armilar” in reference to the French watchmaker Antide Janvier who, in the late 18th century, invented a mobile planetary sphere known as Armilar and considered one of his masterpieces.

Another technical feature of the mechanism of this timepiece is the balance spring attached to the balance. Invented by Jacques-Frédéric Houriet in 1814, this variant without terminal curves offers the tourbillon a perfectly concentric beat, thus guaranteeing an improved isochronism. To transmit to this balance spring the impulses corresponding to a frequency of 18,000 vibrations per hour – 2.5 Hz – Vacheron Constantin developed an escapement system consisting of a silicon escapement wheel and a lever with diamond pallets, materials which reduce friction without any need for lubrication, thus increasing the accuracy of the mechanism.

Every detail of the aesthetic finishes of the Armillary Tourbillon Perpetual Calendar ‘Planetaria’ highlights the ingenious astronomical orchestration of time. Two galvanized-treated titanium globes, weighing just 0.12 grams, rotate smoothly on the grainy dial with Roman numerals applied in polished gold. These Haute Horlogerie finishes are framed by a 46 mm rose gold case, secured by a crocodile leather strap.