The Complication of the Universe: The Breguet Marine Équation Du Temps Marchante Ref. 5887 - Mastering Positional Astronomy of our Solar System - on your wirst!

Mar 18, 2018,09:30 AM
 

With the Ref. 5887, Breguet has introduced a real gem of an astronomic (or shall I better state: solar-system?) timepiece: an Équation Du Temps Marchante (or in English: a running equation-of-time complication). Such a complication is a natural complement to a perpetual calendar, as it adds the correct (solar) minute indication to the correct date display enabled by more correct calendar function - correct as seen from the solar system's point of view, that is.

This complication, however, has mostly spent the time(s) forgotten somewhere in the drawers of the watchmakers, as its astronomic background is complex and not easy to grasp, and its practical implications are minor at best (if you don't own a sundial you will likely not notice) - in stark contrast to the perpetual calendar.

With this article I would like to give proper justice to this fascinating complication, which has found an immensely adequate and fitting interpretation with Breguet's recent novelty.



The watch comes in two versions, in rose gold (left, Ref. 5887BR/12/9WV) and in platinum (right, Ref. 5887PT/Y2/9WV). For the purpose of this article I will focus on the latter, since its specific combination of guillochage and colour choice warrants some special attention:



Background: The Fascination for Astronomic Calendar Indications

Astronomic watches are usually a subset of the many watches with a more elaborate calendar function, such as an annual or a perpetual calendar (we disregard specialised astronomic displays such as planetarium dials). They may include a moon phase indication, although this is technically not connected to the mechanisms responsible for the calendar function.

The allure and the popularity of a comprehensive calendar indication extends far beyond the convenience value of having a correct date readily on the wrist. Particularly for us horologically challenged, it is first and foremost a synonym for additional complexity (and all the romance associated with this), and for the life scientists or the philosophically-inclined, it is a reminder that humankind is entirely embedded in and completely subject to the forces of the universe.

This physical environment, or more precisely the solar system, is tricky for us mortals to handle in practical ways that enable us to organise our time, to plan and to coordinate with others. Calendar systems have been devised, revised and perfected (you may recall calendar schemes such as the Caesarian and later the Gregorian calendars), but yet we are not able (at least as long as good old mechanical tools are concerned) to completely track and rightfully capture the succession of days, weeks and months over the course of a year (or more) - we rely on complex and imperfect approximations to the play of universal forces, with a lot of exceptions and scheduled correctional measures necessary.


(Tower clock with auxiliary dial displaying the equation-of-time. Piazza Dante, Naples. The clock dates to 1853)

I believe It is these fascinating implications on our daily lives combined with the apparent intricacies which make more comprehensive astronomical indications worthwhile to pursue, and they also largely explain their popularity.

Now, with calendar functions, as I mentioned already above, there comes a practical benefit - the correct date. But what about the other, more elusive particularity of time -- the apparent and the mean solar time?


What is the Équation-du-Temps?
Our watches and clocks are considered accurate and precise if they consistently follow a their path of time as close and regular as possible. However, one gets instantly irritated (at least most of the year) if one compares the time display on one’s wrist with those controlled by the universe: a sundial for example!

More often than not the indications differ - yet both are correct in their respective context:

  1. The solar time is what we measure with the sundial. It is based upon astronomical determinants: 1 day=1 rotation of the earth using the sun as a reference. This is by its own nature directly determined by current position of the sun (-> hour angle), and thus changes over the course of a year. In other words, a sundial serves as a proxy for the relative position of the sun vis-à-vis the sun (with limited accuracy).
  2. The civil time is what we measure with our watches and clocks and is an approximation based on an idealised orbital model: 1 day=24 hours. It is also devised such so that over the year the differences from apparent solar time would resolve to zero.
The actual difference between solar and civil time is called the equation-of-time (from ancient Latin: aequatio =difference) and serves to display the difference between mean solar time, corresponding to civil or standard hours and minutes, and true solar time, meaning the actual solar hours and minutes. In terms of value, this difference between solar time and civil time varies between +14 min 15 sec (on 11 February) and -16 min 25 sec (3 November; each civil time vs. true solar time).

On just four days a year, civil time and solar time are exactly the same: on 15 April, 13 June, 1 September and on 25 December. Over the course of a year, the equation-of-time balances to zero; therefore, civil time can also be named mean solar time.

Two main astronomical effects are responsible for the above differences and thus determine the equation-of-time:
  1. The elliptical orbit of the Earth (described by Kepler’s laws of planetary motion)
  2. The tilted axis of the Earth
1st phenomenon: Kepler’s Laws - the elliptical & eccentric course of the earth around the sun

The orbit of the earth around the sun is an ellipse that is, however, not centred around the sun. Despite this, the area formed by the segment connecting the earth and the sun always marks out equal areas during equal intervals of time. It follows from this that the speed of the earth relative to the sun must vary throughout its orbit (over the course of the year) between 30.287 and 29.291 km/s.


(Same time intervals t, different position of the earth on the elliptic orbit ((i), (ii) and (iii)), and different distances thus to the sun: since Kepler's Second Law on the Movement of Planets postulates that the segment A described by the sun and the two earth positions (at time t and time t+1) is always the same, the speed of the earth must be different: (i)>(ii)>(iii))

2nd phenomenon: the obliquity (or tilt) of the Earth’s rotational axis

In the civil time model, the earth is not tilted, however, in reality, the axis of the earth is tilted by 23.44°. This means that the equator is different in an earth-centric view than from a celestial view. While an apparently simple fact, the consequences are quite tricky and are better understood if ones considers the maxima and minima first: The sun reaches her maximal deviation (or her extreme positions south and north at the the beginning of June and December, respectively at the solstices), where we observe the longest and the shortest duration of sunshine (depending on whether you are located on the northern or the southern hemisphere). The minimal deviation is reached at the equinoxes when the center of the visible sun is directly over the equator (around 20 March and 23 September) and the length of night and day are equal.



A practical consequence of the obliquity is that the daily shift of the shadow cast by the Sun in a sundial even on the equator is smaller close to the equinoxes and greater close to the solstices.

The addition of the two phenomena exacerbates their individual effects and defines and determines the equation of time, influencing the perfect (civil) daily sine wave amplitude by 7.66 min for the eccentricity and by 9.87 minutes for the obliquity, respectively, with  the tilt of the ecliptic being the more influential one:



Using a different way of presenting the difference, the civil time is a circle, whereas the solar time resembles a kidney:



Given that the sun’s various positions in the sky are reproduced in an (fairly) identical manner on the same dates, watchmakers can “program” them by means of a special cam which captures above equation. It is, not surprisingly from the above, shaped like a an odd, laying ‘8’ (or kidney, if you like) (analemma curve), shaped as a curve representing the angular offset of the Sun from its mean position on the celestial sphere as viewed from Earth.

An almost majestic example of such a mechanism is found in the famous (and tragic) Breguet pocket watch No. 160 known as the “Marie-Antoinette”:



At ten o’clock, the equation-of-time indication displays the actual difference difference between civil time and solar time on a separate subdial scale (note the long, thin blued hand). You can also see the cam which harbours the equation-of-time 'programme':



This cam is read by a lever (you can spot is at about 2 o'clock of the cam) and the corrective value fed into a rather simple display that indicates the difference between civil time and solar time on a separate subdial scale, leaving it to the user to mentally add or subtract the difference displayed in relation to mean time.

For those how want to delve deeper, I invite to read the Wikipedia entry or the educational website on positional astronomy of Fiona Vincent, University of St.Andrews.


Why an Équation-du-Temps Marchante?
The arrangement of an conventional Equation of Time display comes with two inherent issues: (i) it complicates readout and (ii) leads to confusion as to the reference value of the EoT display (civil or solar time).



Breguet’s Marine Équation Marchante Ref. 5887 supersedes such concerns. It simultaneously indicates civil time and solar time by means of two separate minutes hands: a running solar hand provides a direct reading of solar as well of the civil minutes at once. As the hand is either behind or ahead of the civil minute hand, the reference point is intuitively clear, thereby addressing both of the above mentioned problems in an elegant and easily comprehensible solution.



Again, the context of the initial example of the sundial, the Équation du Temps Marchante combines a clock and a sundial into a single, integrated time display. This integration requires that the solar minutes hand has to meet two imperative demands complicating matters mechanically in a substantial way: it must sweep in a conventional way around the dial, like the civil minutes hand, while also daily moving away from the latter by a distance that varies in accordance with the analemma curve, in order to display the equation.



In their practical implementation, Breguet’s watchmakers made use of a differential gear system that integrates the information provided by two independently operating rotation sources into the mechanisms of the solar minute hand: the passing of civil time, conventionally driven by the pace of the movement, and the solar time correction values which are read from the equation of time can with the help of a lever and mechanically overlaid on the minute hand's position.

For illustration purposes Breguet has created an educative larger-than-life model of the equation-of-time mechanism that nicely shows the mechanical complexity:



The model exposes both the equation-of-time cam and the lever (first image below) as well as the differential gears (second image below):





Using this model mechanism, the difference between a conventional and a running EoT can be aptly demonstrated - the utility of the latter is immediately clear in this 4 minute (civil time) video:



Above solution to this was originally developed by Blancpain for their Villeret Équation du Temps Marchante on which the new Breguet mechanisms is based:



This watch was kind of a twin between a conventional equation-of-time and a running one, it displayed the difference to civil time both on a separate scale as well as with a running solar hand:



The famous equation-of-time cam, with months indicated by numbers, to facilitate understanding.




Up and close with the Breguet’s Marine Équation Marchante Ref. 5887
Breguet kept Blancpain’s base mechanism (which includes, as a natural complement, a perpetual calendar) and developed it further, enabling a new dial layout which displays the information in a carefully considered fashion to ensure simple and intuitive linear reading, along with impeccable visual appeal.



The perpetual calendar is a common complication these days, but Breguet has awarded it with the same consideration that made the equation mechanisms so eminently user-friendly: the entire calendar functions can be read on the upper hemisphere of the dial, in an ultimately logical way (from left to right):

weekday (window) - date (retrograde hand) - month (window) - leap year (sharing the same window with the month display):



At 8 o'clock Breguet placed an inobstrusive power reserve indication:



For our horological pleasure (and to make use of their house-complication), Breguet added a 60-second tourbillon with a titanium carriage housing a Breguet balance with a silicon balance spring.



Fascinating if you have the right illumination...



The tourbillon is not of the flying type so cherished by sister company Blancpain, of the more common one suspended on poth sides. With this Breguet however in the manufactur's most recent ultraflat design, which clearly shows ambition...



In terms of finishing we have of course a fantastically executed dial with a superb (but at least in the blue version a bit malicious) guillochage.





At first, I was a bit indifferent (if not to say dissappointed) by the guillochage, as it might lack the densely packed complex lustre we are so used so see from the other works of Breguet, or masters like Kari Voutilainen and Jochen Benzinger. You need to play a bit with the light to fully appreciate the pattern, as with flat (i.e. ‘wrong’) lighting the engraving might appear rather dull.



The case is a refined integration of the brand’s emblematic Marine collection, with its superb wave-form crown protector. the crown itself is matte with a polished and italicised ‘B’:



The full glory, however, is found on the backside; the magnificent Breguet Cal. 581DPE movement with its stupendous engraving of the Royal Louis, a first rank battleship of the French Royal Navy.







For the admirers to have an unobstructed view on the movement, Breguet implemented a peripheral winding rotor to feed the barrels with sufficient energy for 80 hours of autonomy. The rotor is partly flush beneath the back bezel, with a couple of gears picking up its movements and transmitting the energy into the barrel.



Finally, a wrist shot.



The Breguet Ref. 5887 is a watch which keeps its complexity and its refinement hidden under its (beautiful) wraps. It is a watch designed for conoisseurs with an exterior to match. The complication itself is certainly destined to delight those who (i) know about the universal forces which not only have more profound (consider the alternating lenghts of the months, and the leap year problems) but also quite subtle implications (difference between civil and solar time), and (ii) prefer to appreciate and enjoy their masterpieces privately, with leisure.

The equation-of-time subject matter is complex enough and a challenge to explain, and I can just hope to have succeed (partly). It is even more difficult to translate into a practical, beautiful and functional timepiece - the watchmakers at Breguet might have thought about the dwarf lord Gimli in the Tolkien's The Lord of the Rings: "small chance of success, certainty of failure - what are we waiting for?" (slightly adapted, of course).

It is, ultimately, a very philosophical piece. It offers little which helps us through everyday routine, but it reminds us that we a just a very, very miniscule spot in the ocean of existence. The Breguet Ref. 5887 invites us to embrace the universe, to see things is wider contexts and to appreciate our power and their limitations.

"Astronomy is useful because it raises us above ourselves; it is useful because it is grand. It shows us how small is man’s body, how great his mind, since his intelligence can embrace the whole of this dazzling immensity, where his body is only an obscure point, and enjoy its silent harmony."

– Henri Poincare (French polymath, 1854 - 1912)

I for one am deeply grateful to Breguet for having ventured this path to delight (at least) a few amongst us.

Cheers,
Magnus
____________________________

Technical Data Breguet Ref 5887:

Cal. 581DPE:
  • running equation of time, perpetual calendar, tourbillon
  • 80-hour power reserve
  • 4 Hz silicon escapement wheel and inverted lateral lever with silicon horns
  • adjusted in 6 positions
  • 163⁄4 lignes. 57 jewels
  • peripheral winding rotor
  • Movement bridges have been delicately chased to depict in meticulous detail the Royal Louis, a first rank vessel in the French Royal Navy.
  • barrel is adorned with a windrose motif, in reference to astronomical navigation
Aesthetics:
  • gold, engine-turned dial
  • crown topped with a polished “B” against a sandblasted background
  • more open fluting, with visible flanks
  • 43.9mm-diameter case in rose gold or platinum; thickness 11.5mm
  • rose gold version: silvered dial and an anthracite movement
  • platinum version: blue dial and a rhodium-plated movement
  • Water resistant to 100m
Price:
  • rose gold version (Ref. 5887BR/12/9WV): t.b.d.
  • platinum version (Ref. 5887PT/Y2/9WV): t.b.d.


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Comments: view entire thread

 

Captain Nemo's new watch: looks a tad like an UN, in a very positive way

 
 By: COUNT DE MONET : March 18th, 2018-10:45
A remarkable piece! Like the new design of hands and lugs, albeit they look a little like an UN, but I guess if one goes nautical you can not bypass UN.

Very comprehensive review...

 
 By: mdg : March 18th, 2018-10:46
...the complications are interesting, but the presentation is a bit over the top. The anchor for the date pointer, for example, is far too 'cute.' It's in the 'Marine' line...we get it.

Excellent review! I've had this one on the wrist

 
 By: Spangles - Dr. Tabby : March 18th, 2018-11:17
It wears smaller than the almost 44mm would suggest, partly owning to the short lugs. It's very nice in person. I recommend trying it on. People can dig through this Breguet page to find my post with a few pictures on my 6.75" wrist.

Thank you very much Magnus for this superb review. Very educational and in depth

 
 By: Alkiro1 : March 18th, 2018-16:25
What a watch! I definitely prefer the platinum version. The back is absolutely stunning. Best wishes Alkiro

Thank you Alkiro, I knew you would like it ;-) [nt]

 
 By: Ornatus-Mundi : March 19th, 2018-02:48
No message body

You know me well 😉

 
 By: Alkiro1 : March 19th, 2018-04:03
Best wishes Alkiro