Pentax 70511 3.5mm XW Telescope Eyepiece

The Pentax 70511 XW 3.5mm is a premium 1.25" eyepiece engineered for high-magnification astronomical and terrestrial observation. Its optical design employs high-refraction, extra-low-dispersion lanthanum glass elements to control chromatic aberration and deliver sharp, color-neutral views from the center of the field to the edges. Pentax's proprietary smc multi-layer coatings are applied to every air-to-glass surface, suppressing internal reflections and maximizing light throughput — a critical advantage when pushing magnification to levels where every photon counts. The 70° apparent field of view is wide enough to provide comfortable context around your target, whether you are splitting tight double stars, observing planetary detail, or examining fine lunar features.

What sets the XW series apart at short focal lengths is the 20mm eye relief, which remains constant across the entire XW lineup regardless of focal length. Most eyepieces at 3.5mm offer only 2–5mm of eye relief, forcing the observer into an uncomfortable squint against the eye lens. The XW's generous relief makes extended observing sessions practical and accommodates observers who wear glasses. The eyepiece body is sealed to JIS Class 4 weatherproof standards, so dew-laden nights and damp outdoor conditions will not compromise the internal optics. A fold-down rubber eyecup adjusts the eye position for those who observe with or without spectacles. For serious visual astronomers seeking the best possible views at high power, the Pentax XW 3.5mm is a benchmark-level eyepiece.