Perpetual Moon 41.5 Gold

Celestial rays

A white mother-of-pearl star in a midnight-blue sky. The astronomical moon phases showcase Arnold & Son’s creativity and aesthetic flair. Perpetual Moon 41.5 is presented in two new interpretations, in red gold and platinum. Its dial features a unique motif, Stellar Rays, as befits this astronomical complication.

Arnold & Son explores the theme of moon phases with its constant eye for detail and decoration. Two new editions of Perpetual Moontake advantage of the watchmaker’s recent developments in the fields of cases, dials and finishes. These references further enhance the collection of giant moons by this most British of Swiss brands.

Perpetual Moon 41.5 Red Gold joins the permanent collection, while the platinum version is produced in a limited edition of 28 timepieces.

Frame of light

The Perpetual Moon 41.5’s cases in 18-carat (5N) red gold or 950 platinum have been redesigned. The lugs have been simplified so that instead of their original cross shape, they now present a tauter form of plunging bars with bevelled ends. The case, previously measuring 42 mm, is reduced to 41.5 mm without affecting the size of the dial. This has reduced the width of the bezel, drawing attention to the dial, its finishes, and its vast moon.  

Furrows of light

The dials on these new creations present a unique finish known as Stellar Rays, its aesthetic obtained through skilfully irregular engraving. Several depths and widths of rays coexist and follow on from one another, creating their own rhythm, each generating a fluctuating interplay of light and a depth obtained by applying several layers of transparent lacquer.

This unique effect is employed in two forms. Perpetual Moon 41.5 Red Gold is combined with a dense, deep blue adorned with gold edging on the moon aperture, together with golden hands and hour markers. Perpetual Moon 41.5 Platinum is coupled with a salmon pink whose soft metallic radiance complements the rhodium-plated details on the dial.

Circles of light

Realistically depicted with hand-painted shadows, the large moon is enhanced with a luminescent material that is particularly intense in darkness yet invisible in daylight, giving way to the white mother-of-pearl disc. It is set against a blue PVD-treated grained sky and is surrounded by the constellations of the Big Dipper and Cassiopeia, also hand-painted and coated with Super-LumiNova.

The constellations have been chosen as a direct reference to John Arnold’s history as a maker of naval chronometers. The Big Dipper and Cassiopeia have been used by navigators in the northern hemisphere since time immemorial to find their bearings and locate the North Star (Polaris). The position of the latter defines the North and its angular altitude, or position in the North-South plane, and allows the distance to the equator, i.e., latitude, to be estimated.

Accuracy of light

On the case back, a secondary indicator allows the moon phase to be adjusted quickly and precisely. The hand-wound calibre that powers it, reference A&S1512, can track the development of its segments with exceptional precision. The duration of a complete lunar cycle is 29 days, 12 hours, 44 minutes and 2.8 seconds. Arnold & Son has succeeded in representing it in such a way that it would take 122 years for this movement, if regularly wound, to accumulate a day’s difference between its display and celestial reality.

Like all Arnold & Son movements, the A&S1512 calibre has been entirely developed, manufactured, decorated, assembled, adjusted and cased at the Manufacture in La Chaux-de-Fonds. The calibre features two barrels and an oscillation frequency of 3 Hz, providing a power reserve of 90 hours.

Technical specifications

Functions                     

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

Movement

• Calibre: A&S1512, mechanical 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, Côtes de Genève stripes radiating  from the centre
  bridges: polished and chamfered 
  wheels: circular satin-finished
  screws: blued and chamfered, polished heads 
  second moon-phase indicator: rhodium-plated and circular-grained                                     

Dial                               

• ‘Stellar Rays’ decor, with blue PVD treatment

Moon phases                

• sky: grained, with blue PVD treatment
• constellations: hand-painted, with added Super-LumiNova
• moon: mother-of-pearl disc coated with Super-LumiNova, hand-painted details

Case

• Material: 18-carat (5N) red gold 
  
• Diameter: 41.5 mm
  
• Thickness: 11.30 mm
  
• Crystal: domed sapphire, with an anti-reflective coating on both sides 
  
• Case back: sapphire crystal, with an anti-reflecting coating
  
• Water-resistance: 30 m / 3 ATM 

Strap

• Materials: blue alligator leather, hand-stitched
  
• Buckle: pin buckle, 18-carat (5N) red gold 

References 

• 1GLBR.U01A.C200A                                     

Edition

• unlimited
  

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.