Credits: Article and images by Ashton Tracy @ Quill & Pad. See the original article here - https://quillandpad.com/2023/10/05/equation-of-time-eot-what-is-it-and-whats-the-attraction-reprise/
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The current equation of time complication
To successfully track true solar time we must first track mean solar time; then the difference can be calculated and displayed.
Breguet Marine Équation Marchante Reference 5887 in platinum
In modern watches, this is accomplished in two ways. The first is via a subsidiary dial on the watch with a hand that indicates from minus 16 to plus 14 minutes. The subsidiary hand is driven by a kidney-shaped cam whose profile reflects the differences between mean and true solar time.
Throughout the year the difference between the two will vary, and the hand will point to the position on the dial indicating the current difference in minutes; the user must then perform the calculation.
The Martin Braun Eos Boreas was the first wristwatch to make the equation of time complication more accessible to a somewhat broader audience in a stainless steel case
The second way to do this is with a direct-reading “solar” minute hand mounted on a shaft concentric with the normal (mean) minute hand and using the same type of cam as before. The Breguet Reference 5887 pictured above is a good example of this.
The solar minute hand automatically tracks the time indicated by the sun on the same dial and in the same way as the normal minutes. In this instance, the calculation has already been solved and the “normal” dial is easy to read.
This does require a more complex mechanism behind the scenes, though, due to the extra wheels needed to display the time on the same axis. It’s worth noting that the equation of time changes depending on the latitude of your location, meaning watches displaying the equation of time need custom cams made for different areas of the world.
In today’s modern world most of us never need to think about the difference between true and mean solar time; however, like most things in twenty-first-century watchmaking necessity is not the goal; we do it because we can.
Modern watches that are considered ultra-complicated are occasionally still fitted with the equation of time complication. Here, it usually features together with a moon phase and perpetual calendar, tying in with the astronomical theme.
The equation of time complication is not particularly complicated to produce with today’s manufacturing techniques, and considering some of the latest advances in watchmaking it pales into the background.
What equation of time does do is hark back to a period of history I very much admire; a period of ingenuity and mechanical advancement, and one that we would be wise not to forget and to always respect.
* This article was first published on April 24, 2018 at Equation Of Time: What Is It And What’s The Attraction In A Watch?
You might also enjoy:
Breguet Marine Équation Marchante Reference 5887: Equating Time On The Run
Mechanical Computers From Then To Now: Greubel Forsey Quantième Perpétuel à Équation
De Fossard Solar Time Clock: Appreciating An Extreme Achievement Without A Loupe
Credits: Article and images by Ashton Tracy @ Quill & Pad. See the original article here - https://quillandpad.com/2023/10/05/equation-of-time-eot-what-is-it-and-whats-the-attraction-reprise/
