This probably isn’t going to be the most popular opinion ever, but I really think we need to get over this whole complications thing — at least in terms of how we assess watches by the number of complications they have. In the first place, there isn’t a universally applied standard for defining horological complications. This isn’t even about the tourbillon debate anymore — like, is it or isn’t it a complication? I’m so over that, and you should be too. (By the way, it isn’t.) There are some out there who think that the flyback function counts as a complication. That a hacking seconds counts as a complication. Fam, let us be real. And in aid of this realness, let us stop acting like the number of complications is a thing, so we can finally cut the bullshit and look at what’s actually cool about any given watch.

(Seriously, though, where’s all this coming from? You don’t see it elsewhere — no one’s going, like, “This is the best dish ever, it has 85 ingredients!” “This movie ought to win all the awards, it has 33 action sequences!” “I love this dope-ass book because it has 28 plotlines.” Logic — we have it, let’s use it.)

What keeps me up at night about the Vacheron Constantin Les Cabinotiers Celestia Astronomical Grand Complication 3600 is not its 23 complications. (To be perfectly honest, writing this article is what’s keeping me up; also that name, typing out that name is keeping me up.) This watch, which I’m going to call the Celestia from now on for sanity’s sake, is worth all your sleepless hours because it tells three different kinds of time. Do you get how bomb this is? Three different kinds of time, with three different base units, drawn from one oscillator, in one watch. I can’t even think of an analogy that would accurately convey how awesome and difficult this is. Maybe because there isn’t one.

The Celestia tells us mean solar time (also known as civil time), solar time and sidereal time. Civil time is regular, metronomic; you literally set your watch by it. That’s because it’s an entirely manmade construct. That’s pretty much all there is to it.

Solar time is irregular but predictable, kind of like weather cycles, or menopause. Most natural phenomena, basically. This is because Earth is a big bitch, and instead of behaving in ways that would give us perfectly consistent time units — circular heliocentric orbit with an axis of rotation perpendicular to the orbital plane — went and did the total opposite of all those things. Earth is like the primary school teacher making you do your mathematics homework during recess; she doesn’t believe in making things easy for you. Then again, Earth’s refusal to play ball is also what gives us the different seasons and other fun things like tropical beaches and ski slopes, so I guess it’s swings and roundabouts (unfortunate choice of phrase for the kid who was kept in during recess).

Then you have sidereal time, which is the technical term for star time. Just as a solar day is defined as the time between two consecutive zeniths of the sun, a sidereal day is the time between two consecutive appearances of a star at a given position in the sky. It doesn’t matter what star or what position you choose — they’re all far away enough that it doesn’t make any difference, and you still end up with the same resulting time.

The sidereal day is slightly shorter than the solar day for a pretty straightforward reason, which I’m not going to go into. You can watch this YouTube video for an explanation though. It’s made by smart people who actually do science for a living, so you’re in good hands there.

Compared to the 24-hour solar day (mean), the sidereal day clocks in at 23 hours, 56 minutes and 4 seconds, making it a sidereal day 0.997 times the length of a solar day. That’s an approximation; the actual figure has like eight decimal places at least — could be more, my calculator display ran out of space.

The oscillator of the Celestia beats at 2.5Hz (18,000vph), which means it can accurately measure a fifth of a second. All these fifths of a second that are being chopped up by this oscillator are then gathered up and turned into readings of mean solar seconds, minutes and hours by established gear systems that they teach you in watchmaking kindergarten.

Turning them into readings of a completely different set of time units is a big pain in the ass, you guys. Worse than bad seafood, or the ex who won’t lose your number. Worse than a cramped airplane seat, an apoplectic baby in the row behind you, and the lady in the adjacent seat watching The Way We Were at full screen brightness for the third time in an otherwise dark cabin.

The display of sidereal time requires a dedicated gear train that does nothing else. Because of the insane ratios that go with translating solar time units into sidereal time units, it’s easier to derive the sidereal day first and then use multiplying gears to break it down into hours, minutes and seconds. It can be done the other way around too, but the kind of person who’d do that is probably also the kind of person who answers personal ads from the Marquis de Sade whilst keeping weekends free for Christian Grey.

So that’s what Celestia does, as far as sidereal time goes. Now we get to the interesting part. What did I tell you? This watch lit AF.

Related Notes + Observations
– The 122-year-accurate moonphase display is pretty awesome too, simply because the synodic cycle (lunar cycle) doesn’t run in neat multiples of civil time either. The Celestia is like the horological United Nations (only vastly more successful), bringing together different systems of time to form a coherent whole vibrating at a single frequency.

– We’ve seen this level of moonphase accuracy in a number of watches (notably from the Richemont group of watch companies, of which Vacheron Constantin is a part), but it’s still a very welcome sight here.

– The Celestia has a power reserve of three weeks over six barrels, which is pretty damn impressive, since your regular old single-barrel time-only ticker gives out within two days.

– Obviously, since the Celestia is a unique piece, there aren’t gonna be a whole lot of people who get to own this watch, but I like to think that its triple-time concept relates to the different ways that a person can engage with the surrounding universe: civil time for our practical, get-shit-done side; solar time for our wider embrace of the world and its quirks, irregularities, its problems; sidereal time for dreaming big and reaching out with our eyes on the stars.

– You might have expected a bit more chat about some of the Celestia’s other functions, like the indications of tide, sunrise, sunset, all that stuff, but to be honest they’re peripheral cam-driven displays that run off the civil-time gear train. While they are cool, they just aren’t as conceptually interesting as the sidereal time display. Also, I’m shifting my discussion of the functions related to the solar (tropical) year indications to a separate article.

– I haven’t talked about the design of the Celestia at all! I wonder if there’s another watch that I’ll use to frame the expertise of Vacheron Constantin in the aesthetic domain…

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