Monochrome Watches
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Ferdinand Berthoud Chronomètre FB 1L, An Instrument of Astronomical Complexity

The Chronomètre FB 1L invites two scientific giants of the Enlightenment on board and relays the age and phases of our neighbouring satellite with chronometric precision.

| By Rebecca Doulton | 10 min read |

The latest “experimental collection” unveiled by Ferdinand Berthoud during Baselworld 2019 unites the findings of two pivotal scientific minds of the Enlightenment. Closer in nature to an instrument than a watch, two limited editions of 10 pieces celebrate the genius of pioneers Ferdinand Berthoud and Jean-Charles de Borda, men whose discoveries and quest for chronometric precision and the calculation of longitude changed the course of history and gave France’s Navy sway of the seven seas. This year, the Chronomètre FB 1 with its in-house tourbillon movement and constant force escapement incorporates the age and phases of the Moon to become the Chronomètre FB 1L (L for lune, French for moon). A fusion of astronomic and chronometric precision, the FB 1L represents the breakthrough scientific projects that helped determine longitude at sea with ever-increasing accuracy three centuries ago.

Expanding the Chronomètre FB 1 Fleet

Just ahead of the Baselworld launch, Brice introduced the new FB 1L watches and explains the evolution of the Chronomètre FB 1 fleet over the past years, inspired by the consummate precision of Ferdinand Berthoud’s marine chronometers. If you remember, the FB 1 Chronomètre won the coveted Aiguille d’Or prize at the 2016 GPHG, just one year after the brand produced its first watch; a remarkable feat for a niche brand created in 2013 by Karl-Friedrich Scheufele (co-CEO of Chopard). The latest vessel to join the fleet not only displays the age and phases of the Moon but is powered by the constant force of the in-house calibre providing a level of astronomical precision rarely seen in a watch, equivalent to a one-day difference in 577 years of operation.

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If you thought that the watch looks more like a scientific instrument, you are spot on. At the Ferdinand Berthoud stand in Baselworld a reflecting circle was on display in a glass cabinet to show how the design elements of the dial were inspired by this historic instrument. Made in 1772 by Étienne Lenoir following instructions by Jean-Charles de Borda, the instrument was used to calculate longitude at night by gauging the position of the Moon.

Reflecting circle. On display at Toulon naval museum. Photograph by Rama and Wikimedia

A Meeting of Enlightened Minds: Ferdinand Berthoud and Jean-Charles de Borda

Ferdinand Berthoud emigrated from Switzerland to Paris in 1745 at the age of 18. It was an inspired location for a young man of such exceptional talent. The cradle of the Age of Enlightenment, Paris was a hotbed of intellectual and scientific inquiry. The French Academy of Sciences (Académie des Sciences 1666), founded to encourage and protect French scientific research, was at the forefront of scientific developments in Europe in the 17-18th centuries. A prolific writer, original thinker and avid experimenter, Ferdinand Berthoud was a frequent visitor of the Academy submitting patents for his inventions and even contributed a large number of horological articles to the Encylopédie, the most influential publication of the Enlightenment compiled by Diderot and a team of 150 scientists and philosophers.

The “Montre Marine 6” created by Ferdinand Berthoud

Longitude and chronometric accuracy were also prime candidates for Berthoud’s inquiring mind. Although the kudos went to John Harrison for his marine chronometer H4, Berthoud worked tirelessly to improve the precision and performance of longitude clocks. (Reportedly Louis XV asked Berthoud to pop over to England and examine Harrison’s H4 Marine Timekeeper but was flatly refused by the English watchmaker.) Berthoud produced his first marine clock in 1761, duly presented to the Academy. His montres marines no. 6 and 8 enabled the measurement of longitude to less than half a degree and passed their seafaring test with flying colours. The King was impressed and in 1770 he was appointed ‘Watchmaking Mechanic to the King and to the Navy’ and received a commission for 20 longitude clocks for the French admiralty.

An example of “Repeating Circle” invented by Borda – present example attributed to Dartigues, made in 1802. Musée des Confluences Lyon, France

Another frequent visitor and member of the Académie des Sciences was chevalier Jean-Charles de Borda, a mathematician, positional astronomer, physicist, mariner and one of the founding fathers of the metric system who published his method of reducing Lunar Distances for computing the longitude in 1778. Borda is also renowned for optimising the ‘repeating circle’, an instrument designed to measure angular distances by repeating the same observation several times on the circle without returning to zero. Renamed the ‘Borda circle’, this instrument allowed for the transition from the octant (accuracy of 150 nautical miles) to the sextant (accurate to 0.2 miles, or 370 metres).

Although the dial remains relatively uncluttered, there is a lot going on technically. The only things that will remind you of the previous iterations of the Chronomètre FB1 are the distinctive octagonal case design, the small hours and minutes counter placed at 12 o’clock and the elongated central seconds hand with its tip bent by hand to reduce parallax error. The tourbillon is no longer visible on the dial side and the lower half of the dial is given over to the lunar complications.  As you would expect from a watch of this pedigree, the attention to detail is obsessive and running your finger over its multiple angles and planes a true tactile treat.

The hull

Like all the other Chronomètre FB 1 models, the case features an elaborate octagonal profile with a large crown. The case is inspired by the architecture of Ferdinand Berthoud’s marine chronometers, in particular, their gimbal suspension allowing on-board chronometers to maintain a horizontal position. Two portholes on the caseband introduce light and a lateral view of the movement while the selector switch, located between 4 and 5 o’clock, is used to set the age of the Moon (L) or the Time (H). The sophisticated machinery below deck means that the watch does not stop running during the adjustment of the Moon complications and vice versa when it comes to setting the time.

The FB 1L is a large watch measuring 44mm in diameter 13.95mm in height. However, the extremely short lug modules ensure the watch sits snugly on the wrist. Two versions are available. The Far Side of the Moon recreates the mysterious, invisible side of the Moon and its case middle is crafted from sandblasted white gold while the more exposed elements are made from ceramised titanium to avoid scratches. The Far Side of the Moon has a much more contemporary, technical feel to it with its darker palette and matte sandblasted gold surfaces. The polished white gold model with black ceramic lugs, known as the Near Side of the Moon, is more luminous but looks larger. Both dials are protected with a domed sapphire crystal that provides an interesting distortion, which you can appreciate on the chapter ring.

Moon Gazing

As mentioned, the dial surrenders its lower half to the ages and phases of the Moon, two quite distinct measurements. We are all familiar with the Moon phase function illustrating the different lunar cycles, also known as a synodic month – if you want to delve deeper into Moon watches, read our technical article here. A hemispherical Moon, framed by a ring with an arrow, rises up from the dial between 4 and 5 o’clock. The 3D laser-engraved Moon is a realistic rendition of our celestial neighbour, complete with pitted craters – one of which is named after Borda, in honour of his groundbreaking lunar-distance method. The Far Side of the Moon is a faithful recreation of the famous Apollo 11 picture of the invisible side of the Moon. The arrow points to a cut-away area of the dial where you can see whether the moon is waxing or waning, thanks to a moving cam. There is another arrow just above the cut-out on the dial indicating whether the Moon age indicator is rising (up to day 14) or returning (to the new Moon).

Used to the more traditional representation of the moon phases in a disc, this is a novel and somewhat unusual way to represent the waxing and waning of our satellite. Always a lovely function to observe, the phases of the moon were not accurate enough readings for a scientist in the 18th century for astronomical use. The star of the show is the age of the Moon indicator, a far more accurate indicator, which counts the number of days since the last Moon. By combining the age of the Moon with time measured by an onboard chronometer, sailors could consult their nautical almanacs and calculate their longitude with great precision.

To the left of the hemispherical Moon is a raised cartouche shaped like a quadrant with the numbers 1 – 14 and the phases of the Moon depicted on the edge. Day 1 indicates the first day elapsed since the new Moon, while the number 14 represents the full Moon. A toothed feeler-spindle with a steel spring (it looks a bit like a cutter that slides back and forth) at 9 o’clock relays the information of the age of the Moon to the hand. The feeler-spindle arm is inspired by Ferdinand Berthoud’s system to display the equation of time, in which a feeler-spindle arm followed an equation of time cam. In this case, the feeler-spindle arm is used to indicate the age of the Moon. A moving cam on the periphery of the movement regulates the synchronicity between the phases and the age of the Moon and you can get a glimpse of its teeth in the cut-out window at 4 o’clock. The cam activates the feeler spindle, which in turn triggers the larger hand to indicate the age of the Moon. Once the hand has reached the number 14 it takes a retrograde tack and slowly returns to the beginning of the cycle.

In keeping with the rigorous science practised by the men who inspired this watch, the mechanics powering the Moon complications are so precise that only a one-day difference will be remarked in 577 years of continuous operation. Compare this impressive level of accuracy to the average precision of most conventional moon phase displays, which are accurate over a period of 122 years.

Calibre FB-T. FC.L

For the first time since its launch, the calibre FB-T.FC.L features a patented complication to indicate the age of the Moon, although the base of the hand-wound movement, entirely made in-house, is the same as in previous Chronomètre FB models. The original suspended fusée and chain winding device, which dominates the upper half of the movement, delivers a constant force to the escapement ensuring a steady stream of power during its 53 hours of autonomy. There is a power reserve indicator on a recessed plate and the words Chronomètre on the opposite side attesting the watch’s COSC-chronometer certification.

Just to give you an idea of the Lilliputian dimensions of some of the elements of the movement, the chain is made from 474 steel links, has a total of 790 components and measures less than 0.30mm in diameter. The movement also features an inverted one-minute tourbillon with direct-drive seconds to compensate for the variations in rate induced by different positions the watch adopts throughout the day. The area allotted to the tourbillon is extremely large allowing for an extraordinary view of the escapement and the exceptional hand finishes. The movement comprises no fewer than 1,240 components and three half bridges, fitted on stylised pillars, are made from black rhodium-plated silver.


This is a watch for connoisseurs with a scientific bent, a timepiece that relays and honours Ferdinand Berthoud’s constant quest for improved precision in the field of marine chronometry. Far from being a nostalgic piece of memorabilia, the watch is a unique blend of elements borrowed from historic scientific instruments with a contemporary twist. For some, it might come across as a rather cold, calculating instrument, for others, it is a celebration of science and technology in miniature form.

Availability and Price

Both models are presented with a hand-stitched black alligator leather strap fitted with an 18k white gold or titanium double-blade folding clasp. A pin buckle is available on request. Limited to 10 models in each version, the white gold FB Chronomètre FB 1L.1 Near Side of the Moon retails for CHF 265,000 while the titanium FB Chronomètre FB 1L.4 Far Side of the Moon retails for CHF 250,000. More details at

2 responses

  1. Looks like a prototype and they have not quite decided how it should look. Never have understood the moon phase fascination.

  2. This watch has all that horology can give. Technical calibre innovation, state of the art mechanics and a fresh look at what information is important and why. While not typically given to ocatagonal cases, I love this piece and fully appreciate its achievement. The back is no less than an imaginal playground and really gives notice to what minor miracles are being reflected here. White gold is the choice for me, as it brings out an even greater precision in the already mind bending dial. Well written article that was no doubt a challenge to write due to this watches complexity of form and function.

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