How to Set a Moon Phase Watch

Video Transcription

In every way timekeeping was born out of man’s fascination with the Sun and its daily rhythms. The world’s earliest horologists used sundials to inform are now familiar gears and hands. And of all the things they tracked the lunar cycle was one of the most important. Today the moon in its many ways may not seem as crucial as it once did, but for those who are interested there’s the moon phase complication. This is a complication in a watch that reflects the current phase of the Moon as you would see it in the sky, and in this video, we’re going to show you how to set a moon phase. But first let’s define the moon phase complication.

What is a Moon phase

How a moon phase works

By simple definition a moon phase watch is one that relays the 29.5-day lunar cycle by showing the current moon phase in an aperture on the dial. And it’s also worth noting the moon phase complication is also one of the oldest complications. Now there are eight distinct phases of the Moon, but since the likelihood of remembering terms like waning gibbous is small, we’re going to focus on the four main phases of the Moon. They are New Moon, first quarter full moon and last quarter. The cycle of going from new moon, or no moon in the sky, to full moon is called waxing and full moon back to new moon is called waning. The bulk of moon phase watches present the moon’s current phase by using the aperture to hide the remaining part of the Moon, and of course the design of how it is hidden or shown varies from timepiece to timepiece. As it stands there are two types of moon phase complications in watches. The most common is known as the bosom moon phase watch, which takes a graphical approach by physically showing the moon and its various phases inside of a crescent-shaped aperture. The other type is known as a radial moon phase watch, and it uses an indicator hand to track the lunar cycle. We’re going to focus on the bosom moon phase and when it comes to moon phase watches sometimes it’s easier to picture than to describe. So some of our favorite models:

The JLC Master Ultra-Thin Moon

This watch is elegant and refined. With its 18-carat gold case and simple dial design the moon phase plays the leading role in this watch.

JLC Master Ultra-Thin Moon

The OMEGA Speedmaster Professional Broad Arrow Moon phase

True to its nature the Speedmaster was the first watch worn on the moon, so it’s only fitting that OMEGA would add a moon phase complication. The update keeps the watch looking legendary and we think Buzz Aldrin would approve. And of course,

OMEGA Speedmaster Professional Broad Arrow Moon phase

The Patek Philippe Annual Calendar.

This watch is as luxurious as it gets. Not only is this an annual calendar but the addition of a moon phase keeps it out of this world.

Patek Philippe Annual Calendar

How to Set a Moon phase Watch

So how does this beautiful complication work, and how can I set it in my own watch. Before we start setting the moon phase it does help to understand the lunar cycle in a little more depth. As we mentioned earlier the lunar cycle is 29.53 days, so most moon phase watches have a 59-tooth gear. 29.5 times two, and that allows the two identical moons to rotate through the aperture with more accuracy.

Determine Phase of Moon

All the phases of the moon

Now that we have that out of the way we need to determine what the current phase of the Moon is, and this is done by simply checking the internet. Once we have determined the current moon phase and we know whether it’s waxing, which again refers to the cycling of no moon to full moon, or waning, which is full moon to no moon, we can then begin to set the moon phase on the dial.

Next Set the Moon phase

Next set the watch to 6:30, and this is a precaution to make sure that we do not damage any of the mechanisms in the complication. Now we will begin to press the corrector on the case side to advance the moon phase, and as you can see the moon advances a little every time. We recommend counting how many days it’s been since the last new moon or full moon since its easiest to recognize those phases on the aperture. So, let’s say it’s been eight days since the last full moon. Advance the moon phase until it’s a full moon and then press the corrector seven more times to account for seven days.

Lastly Set the Date

Setting the dat and time on Moon phase watch

Then go ahead and set the date on the watch one day behind, as well. Set the time, making sure to cycle through one whole day to get to the correct day. Notice on the watch how the date changes right at midnight, but the moon phase doesn’t advance till just after 1 a.m. Now the date is correct, the am/pm is correct, and so is the moon phase.

All that’s left to do is enjoy this whimsical complication. The moon phase watch brings to life the natural world through stunning watch innovation and it’s a favorite around here. Let us know your favorite and as always thanks for


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