Citizen ATTESA Limited Edition 41.5mm Eco-Drive Watch #BY1000-51L

Model Reference: BY1000-51L

Overview
The Citizen Attesa BY1000-51L is a high-end execution of Citizen's radio-controlled moon phase technology. While it shares the "Moon Reader" DNA of the Tsuki-yomi, it is elevated by the superior fit and finish of the Attesa line. It features a special edition blue dial inspired by stained glass, providing a sophisticated, multi-tonal shimmer. Crafted entirely from Super Titanium™ with a slimmed-down 41.5mm case, it is designed to be the ultimate daily driver for someone who wants astronomical complications in a refined, "Made in Japan" package.

Technical Specifications

Case Size: 41.5mm (Noticeably more compact and cuff-friendly than the 43mm Tsuki-yomi)

Case Material: Super Titanium™ (Duratect TIC treated for a high-gloss, scratch-resistant silver finish)

Movement: Eco-Drive (Caliber H874; World’s first fully automatic radio-controlled moon phase)

Crystal Type: Sapphire Crystal (Dual-sided anti-reflective coating for "invisible" glass)

Water Resistance: 100 Meters (10 ATM / 333 feet)

Dial: Special edition blue "Stained Glass" pattern with an automatic moon phase disc at 6 o'clock

Strap: Super Titanium™ bracelet with a tool-less micro-adjustment clasp

Special Features

"Luna Program" Accuracy: Like its siblings, it receives atomic signals to perfectly align the moon phase. You never have to manually set the moon; the watch "reads" the date and positions the moon disc itself.

Premium Attesa Finishing: The case and bracelet feature sharper facets and a higher level of polishing than standard models. The Attesa line is 100% manufactured and cased in Japan.

Fit-on-the-Fly Clasp: Unlike the Tsuki-yomi, this Attesa features a clasp that allows you to micro-adjust the bracelet length instantly without tools—perfect for when your wrist expands in the heat.

Stained Glass Dial: Rather than the literal crater texture of the Tsuki-yomi, this dial uses geometric patterns and varying shades of blue to mimic light passing through cathedral glass.

Northern/Southern Hemisphere Toggle: Allows you to change the moon's phase orientation to match your specific view of the night sky.

Global Atomic Sync: Automatically updates time and date via radio towers in North America, Europe, China, and Japan.

Luminous Sophistication: Slender baton indices and sword hands are treated with luminous material, offering a more formal look while remaining functional in the dark.