Perpetual Moon 41,5 Steel Black

Perpetual Moon 41.5 Steel “Colours of the Moon”

The colours of the night 

Like all Arnold & Son creations, the new Perpetual Moon “Colours of the Moon” celebrates the art of watchmaking inspired by one of the Maison’s three principles – Astronomy, Chronometry and World Time – in a homage to its founder, John Arnold. With its “Colours of the Moon” series, Arnold & Son showcases astronomy. Presented in limited editions of 18 pieces each, these three steel versions introduce a world first in watchmaking: the use of mother-of-pearl coloured using a PVD process for both the dial and the moon phase sky. Dedicated to our natural satellite, they feature a mother-of-pearl moon-phase disc with remarkable astronomical precision. It is luminescent and crafted in three shades inspired by the changing hues of the Moon in certain seasons or under exceptional conditions.

A question of encounters 
The moon played a discrete but decisive role in John Arnold’s career. In 1768, after presenting King George III with a sophisticated watch ring, the watchmaker came to the attention of the Astronomer Royal Nevil Maskelyne, who was researching solutions for calculating longitude using the lunar distance method. Rather than copying John Harrison’s famous H4, Arnold decided to innovate and develop his own marine timekeeper. Impressed by the precision of Arnold’s work and a watch he had recently altered at his request, Maskelyne trialled it on a scientific expedition to the West Indies in 1769. This recognition led John Arnold to offer the Board of Longitude a chronometer – a term he invented himself – that was accurate, affordable and reproducible, designed for use at sea.  

A nod to human history
The fifth-largest satellite in the solar system, the Moon has fed the human imagination since the beginning of time. The regularity of its cycles made it humanity’s earliest measure of time, long before the rise of scientific astronomy.

Celebrating the moon
From an astronomical perspective, a lunation – the time between two new moons – lasts on average 29 days, 12 hours, 44 minutes and 2.8 seconds. The full moon marks the culmination of this cycle, and its changing colours have fascinated civilisations around the world throughout history. Depending on its position in the sky and the season or atmospheric conditions, our satellite can assume surprising hues.

It is from these celestial phenomena that Arnold & Son drew inspiration for the “Colours of the Moon” limited editions. The Blue Moon evokes both the rare occurrence of an additional full moon within a single season and the cool tones that certain atmospheric particles can impart to it. The Golden Moon recalls the warm glow the Moon takes on when low on the horizon, its light filtered by the Earth’s atmosphere, a sight often associated with harvests and folk traditions. As for the Red Moon, it alludes to lunar eclipses, when the Earth casts its shadow across the Moon, and only the Sun’s red rays pass through the atmosphere, giving rise to the spectacular “Blood Moon”, steeped in myth and symbolism in many cultures. 

To enhance the moon, Arnold & Son has applied Super-LumiNova beneath the coloured mother-of-pearl representing it. On either side of the lunar disc, the constellations Cassiopeia and Ursa Major are hand-painted in the same luminescent material. These constellations were chosen as a tribute to the mariners who relied on them to locate the Pole Star, which indicates north. 

The choice of stainless steel
Another distinguishing feature of these new “Colours of the Moon” models, which reinterpret the Perpetual Moon collection, is their stainless-steel case measuring 41.5 mm in diameter and 11.67 mm thick, giving this highly exclusive series, limited to just 18 pieces per version, a unique identity. The steel highlights the richness of the dial and the play of light across the moon phase while lending the watch greater versatility for everyday wear without diminishing its horological exclusivity.

A unique manufacturing process 
Always seeking to innovate, Arnold & Son is the first watchmaker to employ a PVD (Physical Vapour Deposition) treatment with mother-of-pearl. Performed in a controlled vacuum environment, this process involves applying a thin metallic layer to the material to add depth and nuance. It provides the dials and moon-phase skies of the Perpetual Moon “Colours of the Moon” editions, in black, blue, or green shades with unique, changing reflections. As light passes through mother-of-pearl, it reveals the natural layers of this precious organic material. And as the light shifts in angle and intensity, the patterns that emerge recall the flowing grain of Damascus steel.

Bringing celestial mechanics to life
To bring this celestial mechanism to life while ensuring everyday timekeeping, Arnold & Son has equipped the three Perpetual Moon “Colours of the Moon” limited editions with its in-house A&S1512 manual-winding calibre. With a diameter of 34 mm and a thickness of 5.35 mm, this movement offers a generous 90-hour power reserve when fully wound.

Luxury finishing
Visible through the sapphire crystal case back, the calibre demonstrates meticulous attention to detail in its finishing, from the 3 Hz regulating organ to the bridges adorned with radiating Côtes de Genève and hand-bevelled edges, as well as the perlage of the main plate and the snailing of the wheels. This opening also reveals blued screws with polished, chamfered heads and a secondary moon-phase display with graduated markings, allowing precise adjustment of the astronomical display visible on the dial side.

Classic styling
In keeping with their striking aesthetic character, the Perpetual Moon “Colours of the Moon” timepieces are paired with hand-stitched alligator leather straps in matching tones. They are fastened with traditional pin buckles in the same stainless steel as the case.

Technical specifications

Functions                     

• hours, minutes, astronomical moon phase, second moon-phase indicator on the case back

Movement

• Calibre: A&S1512, with manual winding
  
• Jewels: 27
  
• Diameter: 34 mm
  
• Thickness: 5.35 mm
  
• Power reserve: 90 hours
  
• Frequency: 3 Hz / 21,600 vph
  
• Finishes               
  mainplate: rhodium-plated and circular-grained
  bridges: chamfered, radiating Côtes de Genève
  wheels: nail-finished
  screws: blued and chamfered, polished heads
  second moon-phase indicator: rhodium-plated and rimmed                                 

Dial                               

• material: PVD treated mother-of-pearl in black

Moon phases                

• sky: PVD treated mother-of-pearl in black
• moon: mother-of-pearl discs tinted red, gold or blue added with Super-LumiNova
• constellations: hand painted, added with Super-LumiNova

Case

• Material: stainless steel
  
• Diameter: 41.5 mm
  
• Thickness: 11.67 mm
  
• Crystal: domed sapphire with a double-sided anti-reflective coating 
  
• Case back: sapphire crystal, with an anti-reflecting coating
  
• Water-resistance: 30 m / 3 ATM 

Strap

• Materials: black alligator leather
  
• Buckle: pin buckle, stainless steel

References

• black: 1GLBS.M02A.C672S

Limited edition

• 18 timepieces
  

Astronomy, Chronometry and World Time

Arnold & Son's three founding principles

Throughout human history, measuring time has always referred to the stars. It was by observing certain stars and understanding their cycle that the first calendars were established with impressive accuracy. It took several millennia before this precision was enclosed in a timepiece like the ones designed by John Arnold. 

The golden age of maritime explorations and discoveries ushered this precision into a new technical ideal – determining longitude at sea. Its immediate corollary was the identification of local time, which changed constantly as the observer moved along an east-west axis. Astronomy, chronometry and what we now call world time are thus inextricably linked within one and the same question, to which John Arnold and his son devoted their lives, their art and their genius. 

This is how these three dimensions – astronomy, chronometry and world time – have come to be embodied in the House's contemporary timepieces.  Echoes of John Arnold's inventions and preoccupations, these pillars represent the foundations on which the Arnold & Son collections are based.

Chronometry: Be accurate

Rate accuracy, which is known as chronometry, is the key requirement of Arnold & Son's contemporary watchmaking. It is the standard of excellence for its collections, the first condition to be met and constantly checked, whether it is at the forefront or in the background of a watch designed by Arnold & Son. It is the most discreet of a movement's characteristics. 

When building an Arnold & Son collection, all the thinking is focused on this chronometry. The manufacture calibres are based on advanced technical fundamentals that are not necessarily the best known. One of them is the choice of small, lightweight balances capable of rapidly returning to their isochronous rate after the latter has been disturbed by inevitable everyday shocks. Another is the routine use of large barrels or even two series-coupled barrels to store the energy required for the movement to function.  They consequently provide Arnold & Son's manual winding calibres with above-average power reserves of 90 hours and more. A third is the particular attention paid to manufacturing the gear trains, roller-burnishing the pinions and polishing the gear teeth, as well as the precision of the machining and therefore the relative positions of the moving parts, a key concept in rate accuracy.

The tourbillon (or the fact of putting the regulating organ in rotation on its axis to best adjust the effects of gravity on the balance and its hairspring) was patented after John Arnold's death, but it was undoubtedly at the heart of his chronometric research and discussions with his friend Abraham-Louis Breguet, who incidentally assembled his first tourbillon on a John Arnold pocket watch in homage to this great watchmaker. Nowadays, the tourbillon has become a must in Arnold & Son collections.

While the tourbillon was not a complication in John Arnold's time, constant force underpinned the design of his marine chronometers. The regularity of the rate of the sprung balance relies on the consistency of the energy that it receives. However, this naturally fluctuates due to the circular and spiral nature of the mainspring contained in the barrel. To achieve a perfectly smooth torque, in other words a constant force, Arnold & Son uses a one-second constant-force mechanism. Housed just before the escapement, it stores up a small but always equal amount of energy in a secondary spring, the remontoire. Thus, every second, the sprung balance receives very precisely the same force to power its oscillations. These become more even, thereby creating the conditions for a high-precision rate.

Arnold & Son also works with another of John Arnold's historical chronometry indicators: deadbeat seconds, a mechanism that was indispensable to navigators at the time for calculating longitude. This mechanism advances one step each second, rather than six or eight smaller jumps in sync with the frequency of the balance. Instead of the term deadbeat seconds, Arnold & Son prefers a name whose very sound means accuracy: “true beat second”. Its jump is a signature of John Arnold's marine chronometers and a complication that is still alive and well in the House's collections.

Astronomy: Under the sky

The Pole Star, Southern Cross, astrolabes and sextant: measuring time has relied on the recurrence of astronomical phenomena in order to find long, reliable points of reference there that can be used under any conditions. The fruit of the human ingenuity, patience and dedication of countless observers and astronomers from every culture, these markers of cyclical time are foundational for Arnold & Son watchmaking.

Astronomical complications are a signature of Arnold & Son collections, with the moon as the heavenly body of choice, main subject and major inspiration. The distinctive feature of the Brand's moon phase timepieces is that they feature “astronomical” display precision as a matter of course. This term corresponds to an accumulated one-day deviation in the moon phase display every 122 years. Since setting this complication requires great finesse, the Arnold & Son moons generally have a double display with a secondary indicator on the case back next to the movement. This extremely rare display bears witness to Arnold & Son's involvement in all types of development and reflects its favoured themes, which are as much chronometric as astronomical.

Over and above their precision, Arnold & Son's moon phases attract all the light, either with a large moon opening up over half the dial, or with a 12-mm three-dimensional rotating moon, making it the largest of all moons. Whether in two or three dimensions, the moon is always treated as a small work of artistic craftsmanship, composed of materials that are rare in watchmaking such as marble or Paraíba tourmaline, or delicate such as mother-of-pearl, meteorite or aventurine glass. The Arnold & Son moon also shines at night, often with a subtle addition of luminescent material. 

World Time: Here, elsewhere, everywhere

With ocean navigation, humankind divided up the world and invented longitudes, which were calculated by comparing the local time, observed using the sun, and the time at a starting point, kept by an extremely reliable timepiece. John Arnold was one of the leading suppliers of chronometers to the British Navy. He was the one who successfully improved the reliability and simplified the production of these indispensable marine chronometers, so much so that he became a benchmark among great explorers such as James Cook and later Dr David Livingstone. The indication of several time zones is therefore integral to Arnold & Son's watchmaking identity.

As this navigation was itself inseparable from cartography, for this world time complication Arnold & Son has chosen to depict a three-dimensional terrestrial hemisphere, making it possible to tell what time it is at any point.

In parallel to this graphic vision, Arnold & Son has developed a second approach to the time elsewhere in the world: with a double tourbillon featuring two distinct rotating regulating organs, making it possible to follow time zones offset by 15, 30 or 45 minutes compared to a full hour – a freedom in terms of setting that remains extremely rare. 

Once again, and because this double display is based on a profoundly chronometric complication, Arnold & Son’s fundamental principles are interwoven. One never advances alone; there are always two – if not three – together. This is how a pillar's strength is measured: it relies on the next one, creating the conditions for a solidity that stands the test of time.