New Releases Watches

Citizen Tsuki-Yomi A-T Brings the Moon to Your Wrist with Atomic Precision

Citizen 'Tsuki-yomi' Radio-Controlled Moonphase

Watchmaking has two very distinct sides. On the one hand you have mechanical watches that speak to our nostalgia and wonderment at clockwork and beautifully crafted machines. On the other hand, you have those watches that seek to be as scientifically accurate and precise as possible by any means and embrace the capabilities of electricity and digital mechanisms. That leads us to the Citizen Tsuki-Yomi A-T, the world’s first light powered analogue moonphase regulated by atomic timekeeping.

Now, there sure are a lot of words in “light powered analogue moonphase regulated by atomic timekeeping” but what it essentially comes down to is that Citizen have created a new moonphase eco-drive movement. Eco-drive is their term of a quartz movement that has its battery charged by light, making it one of their most reliable, accurate and sustainable types of calibre. Where the atomic timekeeping comes in is that the movement, called the Eco-Drive Cal. H874, is equipped with a multi-band radio receiver that picks up signals emitted from atomic clocks (the world’s most accurate timekeeping devices) around the world to ensure constant accuracy.

Citizen 'Tsuki-yomi' Radio-Controlled Moonphase

What’s more, the use of these radio signals means that the Citizen Tsuki-Yomi A-T knows where in the world you are. Which means it will automatically adjust to the local time zone without any manual alteration. It will even adjust the moonphase when you hop between the northern and southern hemispheres since the phases look different once you cross the equator. Since we’ve already talked about the movement so much, let’s wrap this up by mentioning that it has a power reserve of 2.5 years without additional light charging and an accuracy of +/-15 seconds per month without signal reception. The fact that those are worst case scenario stats is pretty impressive showing it still operates to a high degree without its main systems in place.

Citizen 'Tsuki-yomi' Radio-Controlled Moonphase

Let’s zoom out now and talk about the structure and aesthetics of the watch. The case is 43mm in diameter and is made from Citizen’s Super Titanium material, which is titanium that has undergone a Duratect surface-hardening treatment. It has a round design with a gentle sloping bezel and facetted lugs. At 43mm it’s obviously pretty large but that’s offset by the light weight of the titanium.

Citizen 'Tsuki-yomi' Radio-Controlled Moonphase

As for the dial, there are actually three versions of the Tsuki-Yomi A-T, one in grey, one in blue and one in red. Those colours are apt because the background of the dial is an image of the moon. So you have the regular moon in grey and then the famous blue moon and blood moon as the three variations. Beyond that, the dial features the actual moonphase indicator at 6 o’clock, a day/night indicator at 9, a date at 4 and a combined days of the week, power reserve and hemisphere indicator at 12 o’clock.

Citizen 'Tsuki-yomi' Radio-Controlled Moonphase
Citizen 'Tsuki-yomi' Radio-Controlled Moonphase
Citizen 'Tsuki-yomi' Radio-Controlled Moonphase

The more I look at this watch, the more I like it. I know that in the introduction I set out that it’s often mechanical watches that capture our imagination more so than quartz one but this watch bucks that trend. The way it depicts the moon as accurately as possible is in the spirit of scientific research and space travel. People have always yearned for the moon and the Tsuki-Yomi A-T brings it to your wrist with the utmost precision. All for just £595.

Price & Specs:

  • Model: Citizen ‘Tsuki-Yomi’ Radio-Controlled Moonphase
  • Ref: BY1010-57L (deep blue)
    BY1010-57H (silver)
    BY1018-55X (red)
  • Case/dial: 43mm diameter x 10.9mm thickness, titanium case, black DLC coated bezel (red), blue, silver or red dial
  • Water resistance: 100m (10 bar)
  • Movement: Citizen calibre H875, quartz movement
  • Power reserve: 2.5 years o full charge
  • Functions: Hours, minutes, seconds, moonphase, date, days, power reserve indicator, day/night indicator, hemisphere indicator
  • Strap: Titanium bracelet
  • Price/availability: £595

Leave a Comment



About the author

Michael Sonsino

As Digital Editor for Oracle Time, Michael needs an eye for detail, which makes it a good thing that his twin joys in life are miniatures and watches. He's a lifelong fan of fine timepieces, especially those of a more historic nature - if it has a twist of Art Deco, all the better. Recent purchase: Seiko Prospex 1959 Alpinist Modern Re-Interpretation. Grail watch: Vacheron Constantin Historiques American 1921.