Pentax XW 3.5mm Eyepiece 1.25 inch 70° Waterproof

At a dark-sky site, you point your telescope toward a globular cluster and swap in the Pentax XW 3.5mm eyepiece. Instantly, the cluster resolves into a swarm of pinpoint stars across a wide 70° field. This premium eyepiece is built for high-magnification planetary and deep-sky viewing, delivering edge-to-edge sharpness with no compromise.

Key specifications

• Focal length: 3.5 mm
• Apparent field of view: 70°
• Eye relief: 20 mm
• Barrel size: 1.25" (31.7 mm)
• Optical design: 7 elements in 5 groups
• Glass type: High-refraction, low-dispersion Lanthanum glass
• Lens coatings: Fully Multi-Coated (SMC)
• Waterproof rating: JIS Class 4 (splash-proof)
• Filter thread size: M28.5 x 0.6
• Rubber eyecup: Yes, twist-up
• Parfocal: Yes (within XW series)
• Colour: Black

Why choose it

The XW series is renowned for its exceptional optical quality. Lanthanum glass elements and Pentax's proprietary SMC coatings virtually eliminate chromatic aberration and internal reflections, ensuring high contrast and true colour rendition. The 20 mm eye relief is comfortable even for eyeglass wearers, and the twist-up eyecup allows precise positioning. Its waterproof construction means you can observe in dew-heavy conditions without worry.

Ideal use cases

• High-magnification lunar and planetary observation
• Resolving globular clusters and tight double stars
• Observing in humid or dewy environments
• Eyeglass wearers needing generous eye relief

Good to know

The eyepiece is parfocal with other XW models, so minimal refocusing is needed when switching.