Moonphase Watches, and the Importance of Tracking the Moon

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Moonphase Watches, and the Importance of Tracking the Moon

This mechanical watch complication allows you to track the phase of the moon graphically in real time. At the same time the hour and minute hands standard to all watches allow you stay synced with the sun.

In modern times you can consult an app or website to check on the phase of the moon. Maybe you’re curious when the next full moon will be, or what point in your, or your partner’s menstrual cycle it is.  If you’re tired of consulting electronics, you can step outside every night and look. However, the mechanical moon cycle watch allows you to tune in with the moon even during the day, inside, or when it’s cloudy without the use of any electronics.

The Moon’s Effect

The moon has an incredible effect on the Earth and every living being on it. Its gravitational influence produces the ocean tidesbody tides, and the slight lengthening of the day. Most people know about the North star Polaris. Currently, the Northern Pole of the earth points to it. Many people also know that the Earth spins on its axis a little over once each day. However, the Earth has another axis. It’s called precession of the equinoxes, and it’s caused by the moon and sun’s gravitational pull on the planet. It takes about 26,000 years to complete one cycle or rotation. The earth also wobbles in it’s rotations based on many factors including the Moon’s gravitational effect of water change on continental masses.

Precession of the Equinoxes

Axial precession is the trend in the direction of the Earth’s axis of rotation relative to the fixed stars, with a period of 25,771.5 years. This motion means that eventually Polaris will no longer be the north pole star. It is caused by the tidal forces exerted by the Sun and the Moon on the solid Earth; both contribute roughly equally to this effect.

Lunar Calendar

Our current western Gregorian calendar is a solar calendar that was adapted from a lunar calendar. Almost all ancient civilizations’ calendars were based on the moon. The oldest known lunar calendars dating back to 8000 BC, and maybe earlier. 

Although the Gregorian calendar is in common and legal use in most countries, traditional lunar and lunisolar calendars continue to be used throughout the Old World to determine religious festivals and national holidays.

Antikythera Mechanism

The oldest analog computer ~200BC, the Antikythera mechanism, displayed the position and lunation of the moon as a major feature on the front dial.

​Detailed imaging of the mechanism suggests that it had 37 gear wheels enabling it to follow the movements of the moon and the sun through the zodiac, to predict eclipses, and even to model the irregular orbit of the moon, where the moon’s velocity is higher in its perigee than in its apogee.

Lunation or Synodic Month

lunation or synodic month is the average time from one new moon to the next. In the J2000.0 epoch, the average length of a lunation is 29.530588 days (or 29 days, 12 hours, 44 minutes, and 2.8 seconds). However, the length of any one synodic month can vary from 29.26 to 29.80 days due to the perturbing effects of the Sun’s gravity on the Moon’s eccentric orbit.[3] In a lunar calendar, each month corresponds to a lunation. Each lunar cycle can be assigned a unique lunation number to identify it.

This contrasts with the tropical, or sidereal month; the time it takes for the moon to complete one orbit of the earth. In relation to the vernal equinox or stars around us respectively. At around 27.321 days. There are many ways of measuring cycles of the moon as you can read about in the link below:

Month typeLength in days
anomalistic27.554549878 − 0.000000010390 × Y
sidereal27.321661547 + 0.000000001857 × Y
tropical27.321582241 + 0.000000001506 × Y
draconic27.212220817 + 0.000000003833 × Y
synodic29.530588853 + 0.000000002162 × Y

Phases of the Moon

In Western culture, the four principal phases of the Moon are new moon, first quarter, full moon, and third quarter (also known as last quarter). These are the instances when the Moon’s ecliptic longitude and the Sun’s ecliptic longitude differ by 0°, 90°, 180°, and 270°, respectively.[a] Each of these phases occur at slightly different times when viewed from different points on Earth. During the intervals between principal phases, the Moon’s apparent shape is either crescent or gibbous. These shapes, and the periods when the Moon shows them, are called the intermediate phases and last one-quarter of a synodic month, or 7.38 days, on average. However, their durations vary slightly because the Moon’s orbit is rather elliptical, so the satellite’s orbital speed is not constant. The descriptor waxing is used for an intermediate phase when the Moon’s apparent shape is thickening, from new to full moon, and waning when the shape is thinning.

The eight principal and intermediate phases are given the following names, in sequential order:

  • new moon is when the Moon cannot be seen because we are looking at the unlit half of the Moon. The new moon phase occurs when the Moon is directly between the Earth and Sun. A solar eclipse can only happen at new moon.
  • waxing crescent moon is when the Moon looks like crescent and the crescent increases (“waxes”) in size from one day to the next. This phase is usually only seen in the west.
  • The first quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after the waxing crescent phase. It comes a week after new moon.
  • waxing gibbous moon occurs when more than half of the lit portion of the Moon can be seen and the shape increases (“waxes”) in size from one day to the next. The waxing gibbous phase occurs between the first quarter and full moon phases.
  • full moon is when we can see the entire lit portion of the Moon. The full moon phase occurs when the Moon is on the opposite side of the Earth from the Sun, called opposition. A lunar eclipse can only happen at full moon.
  • waning gibbous moon occurs when more than half of the lit portion of the Moon can be seen and the shape decreases (“wanes”) in size from one day to the next. The waning gibbous phase occurs between the full moon and third quarter phases.
  • The last quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after the waning gibbous phase.
  • waning crescent moon is when the Moon looks like the crescent and the crescent decreases (“wanes”) in size from one day to the next.
  • An old moon is a moon with only a tiny bit of it seen in the corner, about to turn into a new moon.

Ancient Maya and the Moon

Ancient Mayans placed great importance on tracking the phase and position of the moon. They had a lunar based ritual cycle called the Tzolk’in that meshed with their solar based agricultural cycle called the Haab. Together they made up the calendar round with a 52 haab year cycle.  They also have a 9 day cycle called the 9 lords of night, and a long count for dating events far in the past or future.

The Mayans also tracked and recorded the lunation whenever adding a date to an important monument. They used 5 glyphs near the end for this.

The stela below is a monument from the Maya city now known as Piedras Negras. It tells the story of a Maya queen named Lady K’atun Ajaw of Namaan.

The inscriptions begin with an introductory glyph that flags to the reader that a date is coming. The glyphs that immediately follow are the long count dates and they show how many bak’tuns, k’atuns, tuns, winals, and k’ins have passed since the world began. These are followed by the specific day from the ritual Tzolk’in calendar. Next comes what is known as the supplementary series, which in this case includes one of nine night gods who ruled each day, as well as a cluster of glyphs to show the precise day within the lunar cycle. Last, the mason carves the day and month of the Haab calendar. In the sidebar you’ll find a translation of the calendar glyphs that start this inscription.


Lunar Series

A lunar series generally is written as five glyphs that provide information about the current lunation, the number of the lunation in a series of six, the current ruling lunar deity and the length of the current lunation.

Moon age

The Maya counted the number of days in the current lunation. They used two systems for the zero date of the lunar cycle: either the first night they could see the thin crescent moon or the first morning when they could not see the waning moon.[25]The age of the moon was depicted by a set of glyphs that mayanists coined glyphs D and E:

  • A new moon glyph was used for day zero in the lunar cycle.
  • D glyphs were used for lunar ages for days 1 through 19, with the number of days that had passed from the new moon.
  • For lunar ages 20 to 30, an E glyph was used, with the number of days from 20.

Count of Lunations

The Maya counted the lunations. This cycle appears in the lunar series as two glyphs that modern scholars call the ‘C’ and ‘X’ glyphs. The C glyph could be prefixed with a number indicating the lunation. No prefixing number meant one, whereas the numbers two through six indicated the other lunations.[26][27] There was also a part of the C glyph that indicated where this fell in a larger cycle of 18 lunations. Accompanying the C glyph was the ‘X’ glyph that showed a similar pattern of 18 lunations.[28][29]

Lunation length

The present era lunar synodic period is about 29.5305877 mean solar days or about 29 days 12 hours 44 minutes and 2+7/9 seconds. As a whole number, the number of days per lunation will be either 29 or 30 days, with the 30-day intervals necessarily occurring slightly more frequently than the 29-day intervals. The Maya wrote whether the lunar month was 29 or 30 days as two glyphs: a glyph for lunation length followed by either a glyph made up of a moon glyph over a bundle with a suffix of 9 for a 29-day lunation or a moon glyph with a suffix of 10 for a 30-day lunation. Since the Maya didn’t use fractions, lunations were approximated by using the formula that there were 149 lunations completed in 4400 days, which yielded a rather short mean month of exactly 4400/149 = 29+79/149 days = 29 days 12 hours 43 minutes and 29+59/149 seconds, or about 29.5302 days.[30]


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