The cold shimmer of a starry night. The diaphanous presence of a large mother-of-pearl moon. The pale gleam of platinum. Perpetual Moon 41.5 Platinum “celestial blue” is expanding the collection’s

different variations on the largest astronomical moon. Every part of this piece evokes the radiance of the night, from the dial stamped with the House’s “Stellar Rays” decor to the moon disc in a grained sky and the navy-blue alligator-leather strap.

Arnold & Son continues to explore the theme of moon phases with a constant eye for detail and decoration. After revisiting the design of the Perpetual Moon, this celestial-blue version is joining the collection. As always, in the backdrop, the moon-phase complication is accentuated to striking effect. In a platinum case measuring 41.5 mm in diameter and 11.30 mm thick, Perpetual Moon 41.5 Platinum “celestial blue” presents the largest of all moons.


This edition showcases the latest characteristics of the Perpetual Moon collection, substantially redesigned to achieve greater refinement and subtlety. The lugs have been simplified and refined. Instead of their original cross shape, they now present a tauter form of plunging bars with bevelled ends. They form a single piece with the case middle, in terms of both their construction and appearance. After remaining at 42 mm for a long time, the case has been slightly reduced to 41.5 mm without altering the dial opening, giving a slimmer bezel instead. As a result, the eye is drawn in towards the dial, its finishes, its immense moon and its dominant pale-blue shade.


The dial is adorned with the “Stellar Rays” finish. Its aesthetic is obtained through skilfully irregular engraving. Various depths and widths of rays are successively combined to create a specific rhythm. Their sequence produces a fluctuating play of light, which is accentuated by the depth created by several layers of transparent lacquer.

The large white mother-of-pearl moon is realistically rendered with hand-painted shadows and coated with Super-LumiNova. It is placed on a grained sky featuring a midnight-blue PVD treatment. Following the tradition of the Perpetual Moon collection, it is surrounded by the Big Dipper and Cassiopeia constellations, which are also hand-painted and coated with luminescent material.

The constellations have been chosen as a reference to John Arnold’s history as a maker of naval chronometers. The Big Dipper and Cassiopeia have been used as points of reference since time immemorial. Midway between these easily identifiable constellations is the North Star. Its position inevitably defines the North and its angular altitude, or position in the North-South plane, and allows the distance to the equator, i.e. the latitude, to be estimated. Before instruments for measuring longitude were invented, it was the most reliable way to determine the position of a boat in the middle of the ocean.


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, is capable of tracking 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 oscillating frequency of 3 Hz, providing a power reserve of 90 hours.