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Moonphase Watches Hold A Universe On Your Wrist

The Celestia 898's moonphase indicator.

From setting to wearing, the moonphase watch is a delight on any wrist.

Complications on watches run the gamut from simple date windows to perpetual calendars, and cover a world of timekeeping in between. But since early man first gazed at the night sky, the moon has held a particular sway over more than just the tide. The moonphase complication, a deceptively simple yet beautiful mark of watchmaking prowess, has often been misunderstood. From how to set a moonphase watch to the history of horology that brought it to the present, we’re here to share with you why this complication puts us over the moon.

THE HISTORY OF THE MOONPHASE – SCIENCE MEETS ART

Before humanity had devices like sundials, clocks, and watches to tell us when we were running late, the passage of time was calculated by observing celestial bodies like the sun, moon, and constellations. By tracking the cycles of the moon, early man “grouped” days into months and conceived the first primitive lunar calendar.

In fact, one of the earliest moonphase tracking devices comes to us courtesy of the Ancient Greeks. Called the Antikythera, it tracked the moon and other astronomical occurrences like eclipses. The Antikythera reigned supreme until the Renaissance, when it became common practice to include a moonphase complication in the clocks created for churches and cathedrals.

These clocks—designed under the premise that Earth was the center of the universe—were quickly rendered obsolete by the science of astronomy, but the moonphase complication was considered an important advancement for both what it depicted and what it said about the clockmaker’s skill level. You have to remember, nothing was off-the-shelf in those days. Everything was carved, crafted, or cast to order, so creating a movement that could track time as well as the phase of the moon’s 29.5 day cycle wasn’t easy.

 

The Celestia 897.
The animated moonphase of the Celestia 897 brings a universe to your wrist.

 

THE MOONSHOT – TRANSLATING A COMPLICATION TO YOUR WRIST

Translating those monthly cycles into a watch-sized movement wasn’t just a matter of coming up with a properly toothed gear or two. That’s because there are two distinct schools of thought when it comes to the moon’s monthly cycles: Sidereal and Synodic.

Sidereal focuses on the time it takes for the moon to completely orbit the earth. Based on a speed of 2,288 MPH, the math works out to be 27.3 days per orbit. Synodic doesn’t have the same need for speed; it’s a phase-based measurement, so Synodic looks at the amount of time between full moons (29.5 days). The extra length takes into account the movement of the Earth orbiting the sun, which forces the moon’s orbit to exceed the normal 360 degrees needed between moons.

Since we’re talking about watches, timing isn’t everything—precision is. So watch experts defer to The Watch Handbook, the horology bible, which marks the lunar cycle as 29.530588853 days. With the cycle defined, the mission became creating a movement that shows the moon’s complete cycle with minimal stress to the host movement’s power reserve. Watchmakers were searching for a solution that was simple in terms of moving parts, yet stunning in terms of accuracy.

A SOLUTION WITH TEETH – THE MOONPHASE LANDS ON YOUR WRIST

The first solution to the moonphase conundrum was a 59-toothed gear that controls the movement of a disk, featuring two engraved/screened/painted moons at the equivalent of 6 and 12 o’clock. To make sure the gear turned once every 24 hours, a micro-lever was designed to connect to the hour-hand. With 59 teeth, the disk would do a full rotation every 59 days—meaning each one of the two moons would go through a “full cycle” every 29.5 days.

But whoever came up with the 59-tooth gear design forgot that the Synodic cycle isn’t exactly 29.5 days. While that extra 0.03 days may not seem like much, they do add up enough so that the moonphase complication lost a whole day’s worth of accuracy every 2 years, 7 months, and 2 weeks. Higher-end watch brands jumped into action, creating a higher-priced 135-tooth model that was engineered to go 122 years before needing their accuracy adjusted. (Of course, this assumes you’re wearing your moonphase watch every day for anywhere between 3-122 years to notice a difference. Fortunately, Stührling owners don’t have that problem as both of our Celestia Moonphase watches are quartz-powered so they stay accurate both on and off your wrist.)

 

The Celestia 898
The Celestia 898 combines a moonphase indicator with day of the week and day of the month chronograph functionality.

 

RAISING THE STAKES (AND INTEREST)

With the advent of formalized calendars and more accurate timekeeping, the moonphase complication swiftly became the “tube in the age of the transistor.” While it had its place and left its mark, the actual utility of the moonphase complication couldn’t match the better, more cost-effective ways of tracking the lunar cycle. Rather than relegate it to obsolescence, watchmakers did what they do best: found a way to refresh its whole perception by integrating the moonphase into other complications.

The first example of this happened in 1925 when Patek Philippe integrated a moonphase complication into their groundbreaking perpetual calendar. Aside from making Patek’s perpetual calendar even more groundbreaking, it also served as a challenge to fellow watchmakers like Breguet and Audemars Piguet to step up their game—and they both launched their perpetual calendar/moonphase timepieces within a decade of Patek’s. Thanks to the added attention—and added value—brands were soon able to spin off the moonphase as a “solo” complication, and the moonphase watch was (re)born.

Lucky for manufacturers, advancements in printing, embossing, 3D printing, and micrography have all been instrumental in making sure demand stays constant. Where moonphase dials used to offer either rudimentary depictions of the lunar surface or the classic “man on the moon” image, the graphics on today’s moonphase dials run the gamut from 3D-textured surfaces to photorealistic micro-engraving.

MOONPHASE SETTING MADE EASY

For all their complicated history, setting a moonphase watch couldn’t be easier. First, figure out what phase the moon is currently in. It’s easiest to set your moonphase on the day that coincides with the full moon, but no one will know if you’re off by a day or two.

Once you know what phase the moon is in, pull the crown all the way out as if you’re setting the time and begin turning. You’ll notice that every time you pass midnight (2 full revolutions around the dial), the moonphase indicator will advance slightly. Simply keep turning until the moon on your dial matches the current phase of the moon. Once your dial is “in phase” with your moonphase source, just set your watch for the correct time and push the crown back to the locked position.

Now you’re all set to bring a galaxy to your wrist. Because let’s face it: it’s 2019, no one is buying a moonphase to make sure they have an accurate way of tracking the lunar cycle. Here at Stührling, we like saying “you don’t wear watches to tell time, you wear them to tell your story.” So consider a moonphase watch a welcome addition to your story, unlocking a world of style and potential.

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