It’s easy to get dismissive of upmarket astronomical watches in this age of cheap digital apps, but it’s still impressive to see what can achieved with mechanical movements – and how that can still sometimes put the apps to shame. For example, we got a look at Swiss watch maker Antoine Martin’s Tourbillon Astronomique watch at Baselworld this week, which can not only tell what time the Sun will rise and set at, but even has a few tricks that you won’t find at the app store.

The creation of Martin Braun, who is known for his Perpetual calendar début watch, the Astronomique is no lightweight. In fact, it seems as heavy as a scuba diver’s watch, but it packs a lot of high-precision features like clockwork sardines inside of its 18K rose-gold case with brown alligator strap and rose-gold deployant buckle.

The first thing that catches the eye on the Astronomique’s silver dial is the prominent window where you can see the silicium escapement for the 52-jewel flying minute tourbillon movement that makes up most of the watch’s 428 individual components. In addition to the pedestrian hour and minute hands, the dial also makes room for a number of displays that look deceptively simple for all the calculation and craftsmanship behind them.

The most important are the sunrise and sunset displays off which most of the other functions set themselves. These displays show the time for sunrise and sunset at a location of the owner’s choice. Since this is a mechanical watch, this means that Antoine Martin has to make some complex calculations and individually craft control cams for the movement for each customer. The owner also gets a table for finding sunrise and sunset for other locations.

Another display is for the sign of the zodiac and season. This is more than just for show. It also helps to make setting the watch simpler because there isn't room in the watch movement for a perpetual calendar, which is replaced by a simple date display with a correct button to synch it to the current month. A version of the season display for the southern hemisphere is also available.

There’s even a display for the equation of time. That is, how many minutes difference there are between clock time and solar time. Since the Earth revolves around the Sun at different times throughout the year, clock time and solar time can disagree by up to 15 minutes. If you're worried about this sort of thing, the Astronomique will oblige. There’s even a day and night display that sits above the dial and lets you know which side of the 24-hour cycle you're in.

Moon phase displays are fairly common in even downmarket watches, but the Astronomique has its own take on it. Instead of a rotating Moon phase, the watch saves space by using a shadow disc that moves across a realistic Moon engraved on sterling silver. The semi-transparent disc doesn't black out the part of the Moon it covers, so the display looks as if the Moon is shining under Earthlight, as it does in real life. There’s also a + and - display to indicate if the Moon is waxing or waning.

On the reverse side of the Astronomique you’ll find the display that shows how much of the six-day power reserve remains, and an engraving of the location that the sunrise and sunset calculations are set for.

Next to this is a very rare feature on wristwatches; a declination display. This is a map of the world and the degrees of latitude with a red line showing where the Sun is directly overhead at noon on today’s date. As the year progresses, the line moves up and down between the Tropic of Cancer and the Tropic of Capricorn, which define the limits of how far north and south the Sun travels in the sky. On the display, there’s also a polar shadow line, which shows the area around the North or South Pole that is in perpetual darkness at the present time of year.

According to Antoine Martin, user-friendliness was a top priority for the Astronomique. Sunrise and sunset times, the sign of the zodiac and season, the equation of time, and the declination display are easily set with the crown in the rapid-setting position, with a single setting locking in all the functions. The correction button is only needed for the date and Moon phase.

Martin Braun tells us that the company is already working on the first order. However, it won’t be cheap with a price tag of CHF500,000 (US$564,000).

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