More so than possibly any other mainstream complication, the moonphase carries a unique position in watch enthusiast culture. Although it’s undeniably evocative and emotional, the moonphase complication itself is arguably divorced from the hyperfocus on precision that dominates most horological thinking; after all, when is the last time you needed to know the phase of the moon down to 1/10 of a second? Of course, brands do love to tout the accuracy and longevity of their moonphases, but from a practical perspective, the complication is less in need of split-second precision than most. On the other hand, resetting a moonphase complication may be the most cumbersome operation this side of a perpetual calendar, with the difference between a waning gibbous and a true half-moon often coming down to guesswork. Citizen’s latest major release interacts with both sides of the conundrum in an unusual way – for the first time in the world, the brand has developed a moonphase watch that also features radio-controlled atomic timekeeping. Beyond the impressive technical advancements, the new Citizen Tsuki-Yomi A-T delivers a bold, contemporary sports watch look, with lightweight titanium construction and unique lunar-inspired visual flair.

The Citizen Tsuki-Yomi A-T’s Super Titanium case offers a case study on how to make a bulky watch feel manageable on the wrist. At 43mm wide and sizably thick, it’s certainly not a small watch in theory, but Citizen uses nearly every tool in its arsenal to make this watch look and feel far closer to 41mm. As a start, there’s the Super Titanium case material itself. With far less weight than steel and a darker, more reserved color, Citizen’s proprietary alloy both markedly reduces the case’s visual heft on the wrist and harnesses some of the well-known slimming power of dark colors to change the wearing experience. Next, of course, is the form of the case itself. Most of the case’s height is distributed between a sloping polished bezel and the broad, flaring polished case side chamfers, leaving only a narrow horizontally brushed mid-case that works to lessen the apparent thickness of the design in profile. The lugs also have a major part to play in this wearing experience. Not only do the dramatic, sharply angled facets give this case a surprising amount of light play for a titanium case, but the clipped, snub-nosed lug tips lead to a remarkably compact lug to lug for a 43mm watch. Taken as a whole, this case design is pure modern Japanese sports watch, but sharply executed and manageably proportioned. At first glance, the broad pump pushers at 2 o’clock and 4 o’clock might be confusing to some enthusiasts, as the Tsuki-Tomi A-T does not have a chronograph complication. Instead,  these pushers (along with multiple crown positions) are used for calibrating the wearer’s current time zone and hemisphere for the atomic-synced main timekeeping display and the moonphase complication. The Tsuki-Yomi A-T may blend sporty aesthetics with a generally un-sporting moonphase display, but Citizen backs up the appearance of this case with a solid 100 meters of water resistance.

When contrasted with the crisp, sharp simplicity of its case, the Citizen Tsuki-Yomi A-T’s dial presents a surprising amount of depth and complexity. The case’s chronograph-esque cues continue through the Tsuki-Yomi A-T’s triple subdial layout at 12 o’clock, 6 o’clock, and 9 o’clock, although each of these displays offers an entirely different function. At 12 o’clock sits the multi-function subdial with a complex terraced chapter ring, operating as either a pointer day display, a power reserve indicator, or a northern/southern hemisphere indicator depending on crown position and pusher use. Of course, the 6 o’clock subdial is dedicated wholly to the watch’s flagship moonphase display, rendered in crisp printed two-tone white and gray against a pure black background. Citizen makes this display the natural focal point of the dial in a trio of ways. The first and most obvious of these is apparent size — this is the visually largest subdial of the three by a sizeable margin, and it naturally draws the wearer’s eye by dint of simple visual weight. Citizen also adds a contrasting black azurage panel to further emphasize the complication and caps off the subdial with a narrow, brightly polished accent ring. Lastly, the minimalist recessed 9 o’clock subdial operates as a simple day/night indicator.

Outside of the ultra-accurate moonphase display, though, the real visual standout here is the main dial surface itself. At first glance, this deep blue dial appears to have a randomly mottled, glossy surface, but once one has a moment to adjust, the Tsuki-Yomi A-T’s most unique stylistic touch comes into view. The entire main dial is covered with blue translucent sapphire, and beneath is a remarkably detailed rendition of the familiar pattern of dark craters and “seas” that make up the surface of the moon. It’s a clever, visually arresting tribute to the first-of-its-kind moonphase advancement on display here, and it’s just abstract enough not to feel jarring on the wrist. Citizen pairs the Tsuki-Yomi A-T’s dial hardware to its sharply angular case design, with clipped-tip dauphine hands coupled to broadly faceted trapezoidal indices. By far the most confusing portion of the Tsuki-Yomi A-T’s design, however, is its black outer chapter ring. Like the 12 o’clock subdial, this ring tracks multiple functions, ranging from the currently displayed time zone (measured in hours ahead or behind UTC), the current daylight savings status, and whether or not the movement is currently receiving its radio-controlled atomic time correction signal. The layout of this chapter ring coupled with the operation of the crown and pushers is surprisingly unintuitive and may prove frustrating to use even for seasoned enthusiasts.

The power behind the Citizen Tsuki-Yomi A-T’s pioneering moonphase display is the in-house H874 Eco-Drive quartz movement. Packing in a perpetual calendar alongside its moonphase display and 24 selectable time zones, the H874 is certainly not light on functionality, and its performance specifications are equally impressive. As long as the H874 receives its regular radio-controlled atomic timekeeping signals, the watch is functionally perfectly accurate across all complications, but even if those signals were to fail for some reason, the movement still provides an impressive +15/-15 seconds a month in accuracy. Likewise, the light-powered Eco-Drive charging system offers exceptional power reserve performance, with up to 30 months of power reserve on a single full charge.

Citizen completes the Tsuki-Yomi A-T with a matching three-link Super Titanium bracelet. While the brushed finishing and polished edge details on the center links tie into the case’s overall finishing solidly enough, the bracelet design itself arguably lacks some of the sharp, angular visual drama of the rest of the watch. With that said, it’s a safe, well-executed bracelet layout, and Citizen’s Super Titanium material makes it eminently light and comfortable on the wrist.

Moonphases are a complex complication in watch culture, often drawing more on their emotional appeal than their mechanical prowess. With the new Tsuki-Yomi A-T, however, Citizen manages to create a sporty, modernist moonphase design that both draws on the evocative power of the moon and delivers the world’s first-ever radio-controlled moonphase complication. This marriage of accuracy and emotion is undeniably compelling and represents a major step forward for Citizen’s mid-tier Eco-Drive designs. The Citizen Tsuki-Yomi A-T is available now through authorized dealers. MSRP for this watch stands at $850 USD as of press time. For more information, please visit the brand’s website.