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Good evening, everyone!
This column discusses mechanical watches from an engineer's perspective. For our 10th installment, the topic is:
"The Structure and Allure of the Moonphase"
We'll be discussing this topic today.
The "moon" plays an indispensable and vital role in the existence of humanity, and by extension, Earth. Humanity has utilized the existence and movement of this important satellite in various aspects of life. Today, with the evolution of technology, many people likely perceive the moon not just as something useful for daily life, but as a mysterious entity, as seen in phenomena like "supermoons" and "total lunar eclipses."
And when it comes to functions related to the moon in the world of watches, we're talking about the "moonphase." It's a romantic feature that tells you the current phase of the moon.
So, this time, I'd like to introduce the structure of the mystical moonphase and how to set it! Please read to the end!
"What is Lunation?"
As the character "齢" (age/days) implies, "lunation" (月齢) refers to the number of days that have passed since that moon was "born."
The "new moon" (the night the moon is invisible) is counted as 0, the next day as 1, the day after as 2, and so on. Around the 15th day, it becomes a "full moon," after which it wanes again, reaching the next "new moon" around the 30th day. This cycle subtly varies in length, typically ranging from about 29.3 to 29.8 days, so it's not perfectly constant. However, for understanding the "moonphase," it's fine to consider it approximately 29 and a half days.
With this in mind, let's explain the main topic: the moonphase mechanism.
Structure of the Moonphase
The popular "moonphase" design features glittering moons and stars set against a deep blue, reminiscent of the night sky.
While there are some unusual types, most designs show a disc with moons and stars peeking through a characteristic semi-circular window.
To read it, a disc with two moons drawn on opposite sides slowly rotates. The displayed moon gradually becomes covered by the round part on the 3 o'clock side, and on the day it's completely hidden, neither moon is visible (new moon). The next day, the other moon begins to peek out from the 9 o'clock side, gradually becoming fully visible, and when it reaches the apex, it's fully displayed (full moon).
Also, the gear of the disc has 59 teeth and is designed to complete half a rotation in 29.5 days, meaning one full rotation in 59 days (clockwise). Although 29.5 days is an odd number, doubling it to 59 days for one rotation simplifies the gear design.
This is the OMEGA x Swatch "MISSION TO THE MOONPHASE" that I recently purchased.
Perhaps to highlight Snoopy drawn on the moon, it's designed so that the other moon, usually covered, is also visible. Looking at this, I think the structure of the moonphase becomes easier to understand.
How to Set the Moonphase
The moonphase changes in conjunction with the watch's time progression, but it can get out of sync due to subtle variations in the lunar cycle or if the watch itself stops. However, if you can check the current moon phase on a website, it's surprisingly easy to set.
*The specific operating method for adjustment (crown or push buttons) and prohibited time zones vary depending on the model and movement, so please check the instruction manual for your watch.
First, let's check the current moon phase.
If you search for "moon phase calendar" online, you'll find various websites, so you can choose any one you like. This time, I'll use "Sunday, July 28, 2024," the article's publication date, as a reference. So, I'll first look for the most recent "new moon" or "full moon" by counting backward from today.
In this case, the full moon on Sunday, July 21st, would be it.
Next, adjust your moonphase to display a full moon. Then, advance the moonphase by "seven days" from Sunday, July 21st to Sunday, July 28th, and you're done.
By the way, if the new moon is closer than the full moon when counting back from the current day, just display the new moon first and then advance the moonphase by the number of days until today.
Conclusion
What did you think?
The "moonphase," which incorporates the mysterious waxing and waning of the moon into a mechanical watch through much wisdom and ingenuity. Perhaps some of you might have thought, "My watch has it, but I never paid attention to the display!" or "It seems difficult, so I've never touched it..."
Once you understand it, I believe it's surprisingly easy, so please take this opportunity to master it!
And... while writing this article, I got news of a new OMEGA x Swatch release!
It perfectly depicts two beautiful moons!
This model will only be sold from August 1st to the full moon on August 20th, after 5 PM during the "blue hour." It's sure to be a battle to get one, but I really want to buy it myself!
I hope this article provided valuable information and sparked even a little interest in luxury watches! Also, if you have any questions, please feel free to ask, and I will be happy to answer them thoroughly. We look forward to your visit and inquiries.
Stay tuned for the next installment! See you then!
