The bond between human beings and the stars is inseparable; what happens in the cosmos cannot be indifferent, and this has been known since ancient times.

Today we are going to talk about the moon phase complication in watches, a particular function that was of paramount importance in the past and that, despite the fact that today technology has made it obsolete, is still one of the most fascinating ever.

The purpose and operation of the moon phase complication

This renowned complication is intended to show the current phase of the moon, thus indicating whether we are in the presence of a new, waxing, full or waning moon, without the need to look at the sky. Now, a question arises: why was this complication invented?

Today’s world has been turned upside down by technology, which has made all kinds of information accessible to everyone, but until 40 years ago, it was very difficult to measure accurately and quickly, phenomena and situations such as, for example, a car race or time zone, without the presence of a clock.

The moon phases came into existence precisely, to provide support in reading the stars, particularly the phases of the moon, which, let us remember, makes one revolution around the earth every 29.5 days.

In reality, the lunar cycle is 29 days, 12 hours, 44 minutes and 3 seconds, which generates a slight deviation, resulting in an error of one day every 2 years and 7 months, a really small value considering the complexity of the calculation.

The use of the function indicating the phases of the moon on watches has thus taken several centuries to perfect, with significant effort on the part of the master watchmakers who have always devoted themselves to its development.

Speaking instead of operation, it is necessary to make an initial distinction regarding the type of movement in that, quartz watches, have, internally, as we know, a printed and programmed circuit board. Whereas, in a mechanical watch, there are gears and wheels that make this function more complicated and technical.

Below the dial of an automatic or quartz watch runs a disk containing two identical moons, which makes one complete revolution every 29.5 days just like the moon’s orbit around the earth. Two moons are used because after this period of time, the second one will appear on the opening of the dial from the left, while the other one will “hide” on the right. This disk has 59 teeth (29.5×2) and advances one notch every 24 hours, thus slowly showing the phases of the moon behind two or three “humps” representing the earth.

Moon phases in antiquity

Since ancient times, man has always sought to understand the solar system so as to measure the passage of time and adapt daily life accordingly. Reading the stars was fundamental because it allowed for orientation in space, the explanation of natural phenomena occurring on our planet, and assisted activities such as navigation, fishing, and agriculture.

In 1999, the Goseck Circle, an archaeological site located in Germany and dating to 4800 B.C., was discovered, which is said to have served astronomical and agricultural purposes. It consists of three apertures, the axis of which coincides with sunrise, sunset at the winter and summer solstice and allows us to understand the importance in knowing the exact position of sunrise and sunset.

The closest depiction to what we notice on modern clocks is the Nabra disk, i.e., a bronze disk 30 cm in diameter in which the sun, thirty-two stars and a crescent moon were depicted. This is the oldest representation of the vault of heaven ever found and dates back to 1600 BCE.

Developments over the centuries

Over the centuries, man has tried to constantly improve the calculation of moon phases, and social and scientific development have contributed to this phenomenon.

Before the advent of clocks, it was the cathedrals with their bell towers that marked time and daily life, so it was essential to implement this complication in such structures, just as was the case with the astronomical clock of Salisbury from 1386 or, to name one known to many, the astronomical clock of Prague located in Old Town Square, dating back to 1410.

As we know the Middle Ages and the centuries that followed as were rich in scientific discoveries, which enabled the further improvement and refinement of the phases of the moon, thanks to figures such as Galileo Galilei and Copernicus, whose thinking revolutionized the previous conception regarding the earth’s orientation.

These scientific developments led to the creation of the first pocket watches in the late 16th century, which soon replaced the reading of time from the old bell towers.

Some of the most famous watches with moon phases

One of the first wristwatches to measure moon phases was the 1925 Patek Philippe 97975, which marked the transition of moon phases from pocket watches to wristwatches. This timepiece was the first perpetual calendar in history, thus integrating the phases of the moon to the display of the day of the week, month and year.

Over the years, almost all maisons have followed in the footsteps of Patek Philippe, such as Jaeger LeCoultre with its Master Ultra Thin Moonphase, Rolex with the Cellini Moonphase or A. Lange & Söhne with the Lange 1 Moon Phase.

The artistry and craftsmanship of watchmakers over the years has grown tremendously, and what was initially counting the phases of the moon has been exaggerated as, for example, happened with the Vacheron Constantin Les Cabinotiers Celestia Astronomical Grand Complication 3600, a watch that is closer to a work of art.

This magnificent timepiece features 23 complications, almost all of which are aimed at calculating celestial phenomena. For example, it is capable of calculating the level of tides through a miniature 3D-printed reproduction of the sun, earth and moon, which are constantly moving. Also shown are the times of sunrise and sunset, indicated by slender hands moving on two graduated scales, as well as the length of day and night, which appears on a special indicator at 6 o’clock.

And that’s not all, because the zodiac signs, seasons, solstices and equinoxes are also featured inside the quadrate, while the constellation as seen from the northern hemisphere has been made on the case back, also integrating the Milky Way. A true masterpiece of engineering and technique.

As anticipated at the beginning of this article, as much as it may be considered a now unnecessary complication, I believe that moon phases will forever represent one of the most fascinating features ever and one that collectors will always be looking for.

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