Testing the Longines Ultra-Chron high-frequency automatic Caliber L836.6

The design of the Longines Ultra-Chron is inspired by the original Longines Ultra-Chron Diver from 1968, the first dive watch with a high-frequency movement.
Apart from the legendary El Primero from Zenith and a few movements from Grand Seiko, there are hardly any serially manufactured calibres with balances that oscillate at a frequency of 5Hz, which is equivalent to 36,000 vibrations per hour. There have been a small number of talking pieces, such as those from Audemars Piguet, Breguet, Chopard, and TAG Heuer, that oscillate at a somewhat speedier pace, but not with consistency and not at affordable prices. That’s why the astonishment sparked in us by the Longines Ultra-Chron was followed by an ‘aha’ moment. The brand can proudly recall its pioneering spirit in the development of watch movements, having turned its attention to high-frequency oscillators a long time ago. 

As early as 1914, Longines created the first high-frequency instrument capable of measuring time to the nearest 1/10th of a second. In 1959, the brand developed the first high-frequency movement for a wristwatch. This observatory chronometer set new precision records. In October 1966, Longines registered the name Ultra-Chron for a timepiece that was more accurate than a COSC-certified chronometer. And in 1968, the Ultra-Chron Diver was introduced as the first dive watch to encase a high-frequency movement, Caliber 431. 

By 1968, if not before, Longines had firmly established itself as a pioneer of high-frequency technology. But in the course of the far-reaching changes in the watch industry brought about by the emergence of quartz technology, Longines stopped manufacturing its own calibres in 1986. Three years earlier, in 1983, Longines had been acquired by SMH (Société de Microélectronique et d’Horlogerie), which later became the Swatch Group. 

Longines’s acquisition by the Swatch Group was not necessarily a disadvantage for the development of the brand’s movements. Various developmental competencies, ranging from fine mechanics and electronics to modern silicon technology, are under the umbrella of movement specialist ETA, which also belongs to the Swatch Group. ETA’s movements are available to various brands that are part of the Swatch Group, but they also serve as the basis for movements that are made exclusively for an individual brand. For example, Longines played a key role in the development of the exclusive L688.2 chronograph column-wheel calibre, which is based on the ETA A08.231 that had been available to the brand since 2009. Another example are the movements for the brand’s recently introduced Spirit collection and especially for the Spirit Zulu Time with GMT function. And last but not least, Longines participated in the development of the new automatic Caliber L836.6, which is a special version of ETA’s self-winding Caliber C07.811. 

Superlative automatic movements with silicon tech 
The brand states, “With centuries of watchmaking expertise, Longines has pioneered numerous technical developments and even today continues to cultivate an unstoppable spirit of innovation. The constant striving for excellence has led Longines to equip all of its automatic timepieces with state-of-the-art movements that have silicon hairsprings.” These are one of Longines’s unique selling points. 

Silicon is not only particularly lightweight and corrosion resistant, it is also resistant to temperature fluctuations and magnetic fields. The material’s physical properties improve the accuracy and longevity of the Ultra-Chron and enable Longines to give a five-year guarantee on this timepiece, which is specially tested before it leaves the factory.

The Ultra-Chron has earned its chronometer certificate from Timelab, an independent Geneva-based laboratory. Timelab’s certification goes beyond the usual chronometer tests, which scrutinise a timepiece’s water tightness, resistance to magnetism, power reserve, and performance on the wrist. The entire watch, not just its movement, is subjected to a 15-day rate test and a series of other tests at three temperatures (8, 23 and 38 degrees Celsius) according to the strict criteria of ISO/IEC 3159:2009. 

A balance with a high frequency of 36,000 vibrations per hour demands much more power from the mainspring than is required by a slower oscillator. Longines discovered this fact when it developed observatory chronometers in the 1960s. One consequence of the high demand for power is that Caliber L836.6 can offer only a 52-hour power reserve. This interval is still acceptable, but undeniably shorter than the 80 hours of power provided by ETA’s Caliber C07.811, which is paced at a frequency of 3Hz and on which the L836.6 is based. The use of a silicon hairspring, which Longines stipulates for its top automatic calibres, compensates for part of the power loss caused by the higher frequency.

Longines’s experience with high-frequency calibres has also shown that faster oscillators offer greater consistency between vertical and horizontal positions, and that the amplitude declines less steeply over the course of a day, which further contributes to their accuracy. Our rate tests on an electronic timing machine confirmed this. The differences among the individual positions were extremely small, ranging between 1.8 and 2.8 seconds. The rate values were excellent, deviating by less than 1 second per day when the watch was fully wound and when being worn. The amplitude fluctuations, on the other hand, remained within the usual range over the course of 24 hours. The rate performance was nonetheless impressive, so the Ultra-Chron has every right to its chronometer certificate. 

Historical design transferred into the modern age 

Caliber L836.6 is a special movement and is housed inside an equally special case with a retro cushion shape measuring 40.8mm by 41.9mm. With polished bevels toward the satin-finished flanks, this new model closely resembles the original Ultra-Chron from 1968, but its case looks slightly more elongated because a divers’ bezel covers its entire middle section. The bezel can only be rotated counterclockwise and clicks into place relatively unspectacularly at half-minute intervals, but the sapphire crystal that covers the rotating ring lends handsome three-dimensionality and a touch of extravagance to the bezel, which gains a professional touch from its full circle of red minute strokes. Longer strokes emphasise the 5-minute marks and luminous Arabic numerals are at three of the quarter hours, completed by a luminous triangle at the 12. This practical arrangement shows the long-standing expertise of the brand. 

The Ultra-Chron was already water resistant to 200 metres in 1968. Its current edition can resist pressure up to 30 bar. The distinctively styled hour indexes atop the grained, matte black dial are nearly identical to the historical predecessor. The four shiny main indexes at the quarter hours are faceted, applied, and flanked by luminous bars. When the bezel is set to its basic position, these indexes are next to luminous numerals at three of the quarter hours and to the orientation triangle at the 12. 

Atop the asphalt-like background of the dial, eight smaller indexes are printed in the form of long white double lines connected by slender crosswise lines. These are not luminous, but each pair of double lines has a luminous stroke next to it at 5-minute intervals in the circle of white indexes around the edge of the dial. The overall result provides excellent legibility in all lighting conditions, including in the murky depths under water. The functionality is further enhanced by the minute hand, which is important for diving and bears a much longer luminous bar than the hour hand. The minute hand’s red colour together with the red scale around the bezel combine to support the watch’s usefulness for diving. The sapphire crystal above the dial is anti-reflectively treated several times and assures that all displays are easy to read. The steep curvature around the crystal’s rim accentuates the retro character of this model. The only drawback with regard to the diving function is that the second hand lacks the luminous tip that was present on the original model.

Our test watch has an elegant, high-quality, seven-row, stainless-steel bracelet whose components are alternately polished and satin-finished. The bracelet is secured by a folding clasp, which is hinged on one side and includes a mechanism that allows you to add or subtract a maximum of 8mm in the length in four 2mm steps. This is not a divers’ extension for wearing the watch over the sleeve of a wetsuit, but only a fine-adjustment option. If you wish, the bracelet can be shortened by asking a watchmaker to unscrew the bars near the clasp. An additional strap made of recycled textile is provided for diving, delivered with the watch in a presentation box along with a special strap-changing tool. You might want a modern quick-change system, which would be relatively easy to integrate at the lugs. But even without this convenience, the Ultra-Chron is a unique and popularly priced timepiece that admirably combines the professionalism of a sporty dive watch with a distinctive historical identity and the pulsating power of a modern high-frequency calibre.

high-frequency movement, 5Hz Calibre 19.73N

A high-frequency movement, 5Hz Caliber 19.73N, enables hand-held stopwatches for sports timekeeping to measure elapsed intervals to the nearest 1/10th of a second. The model shown, from 1922, is a modification with a sweep-second hand. To optimise reading of the 1/10ths of a second, the chronograph’s elapsed-seconds hand sweeps once around the dial every 30 seconds. The 15-minute counter is located on the subdial at the 12.

Modified Calibre 19.73N

Modified Caliber 19.73N has a frequency of 360,000 beats per hour, so a stopwatch that encases it can measure and display elapsed intervals to 1/100th of a second. To achieve this, the chronograph’s elapsed-seconds hand circles the dial once every 3 seconds. The scale along the edge of the dial is divided into 1/100ths of a second. An instantaneous minute counter at 12 o’clock can tally intervals of up to 
3 minutes.


Calibre 24.99, from 1939

Designed to clock ski races, this timepiece is based on a navigational chronometer, Caliber 24.99, here from 1939. The chronograph’s elapsed-seconds hand makes one revolution every 30 seconds. This model is equipped with an additional split elapsed-seconds hand and can tally up to 30 elapsed minutes. The model shown here is a variant for measuring 1/100th of a second. 

Calibre 260

Caliber 260 has a system to halt its balance. This movement indicates hours, minutes, and 1/10ths of a second, and also includes both a flyback function and a split elapsed-seconds hand. The illustration shows a model from 1966 with a special elapsed-seconds hand bearing a vernier scale, visible here as a yellow arc with nine indexes. When this hand is stopped, one of the indexes on the yellow arc will stop exactly on one of the seconds markers on the dial. The number under the corresponding index indicates the number of elapsed 1/10ths of a second. 

Calibre 360

Caliber 360 was the first 5Hz movement for a wristwatch. It was designed for chronometer competitions, built by hand, and manually regulated, with a daily deviation of less than 1/10th of a second.  Two hundred of these calibres were constructed between 1959 and 1963. In 1961, this rectangular movement won first and second place in the precision competition at the Neuchâtel Observatory. 

Calibre 431 with patented dry lubrication

Caliber 431 with patented dry lubrication keeps time with a maximum deviation of just 2 seconds per day. Because this model is far more accurate than a COSC-certified chronometer, it was accordingly given the name Ultra-Chron. Longines patented it in October 1966 and shipped the first Ultra-Chrons to the U.S. in December of that year. 

The Ultra-Chron sports watch introduced in early 1968

The Ultra-Chron sports watch has a red minute hand, water resistance of 200 metres, and was introduced early in 1968 as the first high-frequency dive watch. With the Caliber 431, its rate has an accuracy of 2 seconds per day. The markers on the diving bezel, indexes, and tip of the second hand are filled with luminous tritium. 

This story is already published in WatchTime India Jan-Mar 2023 print issue

Images: Courtesy brand


Longines Ultra-Chron


Compagnie des Montres Longines, Francillon S.A., Rue des Noyettes 8, 2610 Saint-Imier, Switzerland




Hours, minutes, central second hand, rotating divers’ bezel


Longines L836.6 based on ETA C07.811, automatic, 36,000 vph, 25 jewels, Glucydur balance, silicon hairspring, fine adjustment via screws on the balance, Nivachoc shock absorption, 52-hour power reserve, diameter = 25.6mm, height = 4.74mm


Stainless-steel case with bezel with sapphire crystal inset, sapphire crystal anti-reflectively treated several times on both surfaces above dial, water resistant to 300m


Stainless-steel bracelet with folding clasp opening on one side, additional recycled textile strap with pin buckle


Dimensions = 40.79mm (from 6 to 12), 41.89mm (from 3 to 9), 48.31mm (across lugs); height = 13.87mm


3.10 lakhs (approx.)


Longines Ultra-Chron


High-quality stainless-steel bracelet without a built-in divers’ extension mechanism. An interchangeable recycled textile strap and a special strap-changing tool are included. #9



The nonslip bezel locks securely, the screw-down crown is easy to operate and a wristband-changing tool is included with the watch, but the bracelet offers neither a quick-change system nor a divers’ extension.#4



High-quality pillow-shaped retro case based on the historical predecessor, sturdy stainless-steel back, domed sapphire crystal above the dial, bezel with sapphire insert, screw-down crown, water resistant to 300m. #9



Retro design unites with a successful modern interpretation of the original model from 1968. #14



Optimum legibility of the time and the diving function by day and night; the bezel is calibrated all around. #5



High degree of wearing comfort thanks to excellent ergonomics, an appropriately sized case and a high-quality bracelet.#5



This exclusive modern movement combines rare high-frequency oscillation and an acceptably long power reserve; silicon hairspring.#17



Very good rate, well balanced among the several positions and certified as a chronometer.#10



Acceptable price; no other watch in this price class is technically comparable. This modern, professional divers’ watch conforms to the brand’s image. #9


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