So you got one of those watches with a dial that looks like a dashboard instrument — it’s covered in tiny hands, scales, numbers, and complicated-looking stuff that totally overwhelms you. What the heck is all this stuff, and how does one use it, exactly?
What you’ve got in your hands is a chronograph, from the Greek for, approximately, “time writer.” A chronograph is basically a wrist-borne stopwatch, which lets you record elapsed time. They can seem overwhelming initially — like small computers — but once you understand what’s going on within the dial, putting one to use is a cinch.
On the main dial of the watch are you'll likely find several subdials, also known as subsidiary registers or “totalizers.” (Very often there are two to three of these, though in some rare cases, there’s just one.) On a three-hand watch, the seconds hand moves around the dial, giving you a read on elapsed seconds. Not so on a chronograph, however — this hand stays put until you start the chronograph itself, at which point it records elapsed seconds. The “running” seconds hand on the dial is generally moved to one of the subdials — look closely, and you should see a subdial with a tiny hand that’s constantly moving. This is the equivalent of the main, “central” seconds hand on a time-only watch, such as a Rolex Submariner.
As for the other subdials, there will generally be at the very least a “minutes totalizer.” This register records elapsed minutes — often 30 of ‘em, sometimes up to 60. Lastly, on a “three-register” or “triple-register” chronograph with three subdials, there will be an “hour totalizer” that records elapsed hours, almost always up to 12. (So, theoretically, you could time several consecutive football games on your chronograph, or one afternoon’s worth of depositions, or an evening’s worth of your parents arguing about politics.)
Omega Speedmaster Professional
Chronograph bezels vary — oh, a “bezel,” by the way, is the thing inscribed with numbers around the outer periphery of the watch — but very often, the one used will be of the tachymeter variety. What is a tachymeter, exactly? It’s a scale that allows the user to compute things like speed, distance traveled, or the frequency of an event, i.e. number of widgets produced. It’s incredibly useful, and neutral, meaning that the numbers inscribed on one can correspond to miles, kilometers, hot dogs per hour — whatever. More on this in a moment…
Zenith Chronomaster Original for HODINKEE
If you look at the case of a typical chronograph, you’ll notice it has two pushers sticking out the side, flanking the crown. (Some chronographs only have one — these are called, rather fittingly, “monopusher” chronographs.) The top pusher is used to start the chronograph and to stop it, while the button is used to reset it. On a monopusher, the same button is used for stop, start, and reset.
On a very special type of fancy chronograph called a “flyback” — or, in French, a rattrapante — you don’t need to stop and reset the chronograph. A single, secondary push of the top pusher will send the seconds hand “flying back” to zero, restarting the chronograph instantly, making it quick and easy to time successive events.
(*Keep in mind that in rare instances, the pushers are reversed, meaning the bottom pusher is for start and stop, and the top for reset. The Swiss do this occasionally to confuse Americans, which is both easy, and highly amusing to them.)
How to Measure Elapsed Time on a Chronograph
Ok, your horse is up. The starter gun goes off, and ole’ Gluestick is off at a gallop. At the exact moment he takes off, you push the top pusher on your watch, and the central seconds hand begins ticking. Gluestick hauls ass around the track, and when he gets back to the starting line, you depress the top pusher again. You look at the dials on your chronograph, which read thusly: The hand on the hour totalizer hasn’t moved, because your horse has only been running a short while — much less than an hour. The hand on the minute totalizer reads “1,” meaning that Gluestick has been running for at least one minute. The central seconds hand reads “20” seconds (this is read against the main minutes/seconds scale on the dial periphery).
Thus, Gluestick just did a full lap in 1:20. Pretty easy, right?
Now, in order to reset the stopped chronograph, you push the bottom pusher. If you wanted to time a second lap on a standard chronograph, you would have to very quickly stop and then reset the watch, which is generally done using the pointer finger on the top pusher, followed quickly by the middle finger on the bottom pusher. This is imprecise, however — which is why “flyback” chronographs were invented. (See the “Pushers” section above.)
How to Use a Tachymeter to Measure Speed
Ok, here’s the fun part — we’re gonna calculate how fast a Porsche 911 is driving.
First, remember we said that the neat thing about a tachymeter scale is that it can be used to measure any unit, whether kilometers per hour, miles per hour, units per hour, etc? Well, that’s true, but keep in mind that you need the distance calculated to be in the same unit as the speed measured — i.e. you can’t calculate speed in miles across a distance of a kilometer. Said distance would need to be a mile.
So here we go. We want to know how fast our theoretical Carrera is going, and we know that the track it’s driving is one mile long. When the car takes off, we start our chronograph. When it comes around the bend and crosses the start/finish line, we stop the chronograph, which reads 23 elapsed seconds. If you look at the tachymeter scale on the watch’s bezel, you’ll notice that 23 seconds corresponds to somewhere in the realm of 155 units. Thus, the 911 is traveling about 155 miles per hour on average. (“I WANNA GO FAST!”)
How to Use a Tachymeter to Measure Distance
What if we know a given speed, but not the distance traveled?
Omega Speedmaster Professional
If we’re traveling at a constant speed — and the speed must be constant for this to work — you simply start the chronograph at a given point in time. Now let’s say we’re driving 80 mph. When the seconds hand corresponds to 80 on the tachymeter scale (which is roughly at the 45 second mark), you stop the chronograph, marking exactly one mile traveled.
How to Use a Tachymeter to Measure Units Produced
Nivada Grenchen Chronomaster Aviator Sea Diver Chronograph
Let’s say it’s 1943, and you want to know how many Mills bombs a British armaments factory is producing per hour. (Because: why not.) You use your chronograph to time how long it takes to make one bomb, which, for the sake of our example, is 25 seconds. The corresponding number on the tachymeter scale at the 25-second mark is roughly 145. Thus, this factory’s output is 145 Mills bombs per hour. (BOOM!)
Some of Our Favorite Chronographs
Obviously, we love us some chronographs here at Analog/Shift. Here are a few of our favorites:
Omega Speedmaster Co-Axial Master 'Racing' Chronograph IN THE SHOP
Omega Speedmaster: Believe it or not, Omega developed the Moon Watch as a driving instrument, not a space-going instrument. But that didn’t stop NASA from taking one into, well, space. And the rest is history. (NOTE: Certain Speedies have alternate scales, such as a pulsometer, but most feature the famous tachymeter bezel.)
Rolex Daytona IN THE SHOP
Rolex Daytona: Named for the famous raceway of which Rolex has been a sponsor since the early 1960s, this most famous of chronographs is a longtime fan favorite. So much so, in fact, that they’re tough to buy at retail lately — meaning that getting one pre-owned is a fantastic option.
Heuer Autavia 'Viceroy' IN THE SHOP
Heuer Autavia: The cushion-cased Autavia from the 1970s was notable not only for its eye-catching design, but for its automatic Heuer Calibre 11 movement — one of the first automatic chronograph movements in the world. Best of all, they come with all different sorts of bezels, from 12-hour to count-up and more.