Stellar Aspirations A ticking reminder of one s place in the universe, the astronomical timepiece makes a lofty addition to your watch collection.

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1 Left to right: Chopard L.U.C Lunar Big Date ($32,180); Arnold & Son HM Perpetual Moon ($27,845 in red gold). STORY BY BY JONATHON KEATS PHOTOGRAPHY BY JEFF HARRIS Stellar Aspirations A ticking reminder of one s place in the universe, the astronomical timepiece makes a lofty addition to your watch collection. 1

2 AAMONG THE LESSER-KNOWN facets of the famous rivalry between 1920sera industrialists James Ward Packard and Henry Graves Jr. two avid collectors who each ordered successively more complicated pocket watches from Patek Philippe is that both men set their sights on a highly personal complication: They each wanted their nec plus ultra timepiece to feature celestial time with a star chart depicting the sky over their respective homes. While astronomical complications may seem arcane to some, enthusiasts recognize (as Packard and Graves once did) that they touch our primal notions of time, which is why they can still command center stage in the most complicated timepieces today. Even before watches and clocks had minute hands, 17th-century horologists developed gearwork to display moon phases, useful in an agrarian society lacking artificial lighting, yet hardly straightforward since the moon orbits Earth every 29-and-a-half days. Or 29 days, 12 hours, 44 minutes, and 2.9 seconds to be precise and accuracy is the common cause of astronomy and watchmaking. Horologists have approached this mechanical challenge by increasing the fineness of their gearing. On older watches, 59 teeth were cut into a wheel with two full moons each covered in turn an arrangement that lost a day every couple of years. By increasing the number of teeth to 135, watchmakers have improved accuracy significantly. The large classical lunar display on the Arnold & Son HM Perpetual Moon shows the monthly waxing and waning with a lag of just one day every 122 years. That performance is matched by the Chopard L.U.C Lunar Big Date, which presents the lunar cycle on a novel orbital display that shows the various moon phases for both the Northern and Southern Hemispheres. But 122 years is not the mechanical limit. Ludwig Oechslin has developed an innovative new moon-phase module for the Ochs und Junior Moon Phase that deviates by just one day in 3, years. Oechslin achieves this feat by using epicyclic gearing, in which a train of gears controls the rotation of a disc inside an internally toothed hub. The epicyclic gearing and selection of gears within it allow him to impart an extremely precise ratio of rotation between the hour hand and the lunar display: The disc revolves once every days. For Oechslin, this mathematical feat is child s play. He may be best remembered for the trio of astronomical watches that brought Ulysse Nardin s mechanical watchmaking back to prominence in the 1980s and 90s. Recapitulating the early history of astronomy, Left to right: Ulysse Nardin Moonstruck ($125,500 in platinum); Ochs und Junior Moon Phase ($8,000 in titanium). 3

3 Left to right: Blancpain Equation of Time Marchante ($171,300 in red gold); Audemars Piguet Royal Oak Equation of Time ($68,700 in stainless steel). 6

4 the Ulysse Nardin Tellurium Johannes Kepler, However, if you define noon as the time when the sun is highest in for instance, shows the apparent motion of the sky as you would read on a sundial it wanders by as much as the sun, the Earth, and the moon from a terrestrial perspective. The Moonstruck watch by our planet s elliptical orbit and the 23-degree tilt of its axis; this 16 minutes depending on the time of year. The variation is caused Oechslin conceived with Ulysse Nardin a few deviation can be mechanically simulated by the annual rotation of years ago takes up where the Tellurium left a kidney-shaped or ellipsoidal cam that geometrically represents off. Earth is fixed at the center of the dial, seasonal time variation. The Audemars Piguet Royal Oak Equation shown from above the North Pole, with disks of Time elegantly displays the difference by placing a special blued for the sun and the moon orbiting around hand on the same axis as the regular hours and minutes, and orienting the equation to your local solar zenith (which depends on your it. Since Oechslin s mechanism alters the moon phase in tandem with the lunar disk s longitude). The cam rotates the blued hand to the exact minute when rotation, the wearer can see how the moon s your sundial would tell you it is noon. crescent is sculpted by Earth s shadow. More profoundly, the watch tracks global tides, which are caused by the combined gravita-blancpain tional pull of the sun and the moon on the another approach to displaying this deviation. A Equation of Time Marchante takes seas. Of course, the world view shown by special secondary minute hand shows sundial time Oechslin s watch is make-believe, a geocentric throughout the day, rather than only indicating solar model predating Copernicus. Yet the watch noon. Such a running equation is very difficult to also helps to explain why that world view execute mechanically because it requires the hand was so persistent, since the information on the to be oriented by the ellipsoidal cam while it is being rotated by the Moonstruck dial consistently corresponds to regular gear train. For that purpose, Blancpain developed a unique Earth-based observations of the sky above. set of differential gears. Over the course of the year, the solar hand Other astronomical functions reveal how speeds up or slows down to match the path of the sun. our very concept of time is itself a matter Sidereal time, the measurement that drove the star charts of rival of perspective. The complication known as collectors Graves and Packard, differs from both civil and solar time equation of time is especially unsettling, because it derives from the stars rather than the sun. Astronomers since it openly challenges the position of define a day as one complete rotation of our planet on its own axis, the watch s minute hand by showing the as measured by the daily crossing of a fixed star infinitely far from discrepancy between official civil time Earth. Since our standard 24-hour day accounts for both planetary and the time you d read on a sundial. The spin and Earth s rotation around the sun, the sidereal day is ever 24-hour increments of civil time never vary. so slightly shorter: 23 hours, 56 minutes, and seconds. Patek Philippe Sky Moon Celestial Grand Complication, Reference 6102 ($329,600). 7

5 Arnold & Son Left to right: Van Cleef & Arpels Midnight in Paris ($80,000); Jaeger- LeCoultre Rendez- Vous Celestial ($62,000). Audemars Piguet Blancpain Chopard Jaeger-LeCoultre Ochs und Junior Patek Philippe Ulysse Nardin Van Cleef & Arpels Watchmakers seeking to show the night sky must build a special gear train that runs at this minutely faster rate. Sidereal time has been built into the Jaeger-LeCoultre Rendez-Vous Celestial, which builds the daily passage of the constellations in the Northern Hemisphere into a romantic women s timepiece, and the Van Cleef & Arpels Midnight in Paris, which depicts the starry sky specifically over the French capital. Patek Philippe has also revisited the celestial realm with the Sky Moon, a complication whose origins are rooted in the watches made for Packard and Graves and which is now the hallmark of some of the brand s most complex and exclusive watches. Displaying a broad panoramic view of the sky, with an overlaid oval indicating what can be seen from a given latitude and longitude (usually Geneva), the Sky Moon is driven by a mechanism that was first released in the Star Caliber and subsequently miniaturized for the wellknown Sky Moon Tourbillon. The mechanism features an aperture in the deep blue dial opening to a view of the moon with both the phase and angle accurately shown. Packard and Graves had the privilege of carrying their portions of the night sky in their pockets. Only now, with the Sky Moon, can you wear all of it, revolving with the planet, on your wrist. 10