Pentax XW 20 Oculaire 2 cm noir

Under a dark sky, an amateur astronomer swaps eyepieces to frame the Orion Nebula just right. The Pentax XW 20 eyepiece delivers a wide 70° apparent field of view, making it easier to keep celestial objects in sight during long observation sessions. Its 20 mm focal length pairs well with medium to high focal ratio telescopes, offering a balance between magnification and field width.

Key specifications

• Focal length: 20 mm
• Apparent field of view: 70°
• Eye relief: 20 mm
• Barrel size: 1.25 inches
• Optical design: 8 elements in 5 groups
• Lens type: High-refraction, low-dispersion lanthanum glass
• Coatings: Fully multi-coated (Super Multi-Coating)
• Waterproof rating: JIS Class 4 (splash-proof)
• Filter thread: M28.5 P0.6
• Eyecup type: Twist-up rubber
• Colour: Black

Why choose it

Pentax XW eyepieces are renowned for their exceptional optical quality and comfortable viewing. The 20 mm model provides generous eye relief, making it suitable for eyeglass wearers. The lanthanum glass elements and advanced coatings deliver high contrast and minimal chromatic aberration, revealing fine planetary details and faint deep-sky objects. The splash-proof construction adds durability for dewy nights.

Ideal use cases

• Observing large deep-sky objects like the Pleiades, Andromeda Galaxy, and the Orion Nebula
• Lunar and planetary viewing at moderate magnifications
• Comfortable extended viewing sessions thanks to the twist-up eyecup and long eye relief
• Use with telescopes that accept 1.25-inch eyepieces

Good to know

The Pentax XW 20 is part of the XW series, known for consistent 70° apparent field across all focal lengths. It includes a built-in filter thread for attaching nebula or light pollution filters. The eyepiece is fully multi-coated with Pentax's proprietary Super Multi-Coating to maximize light transmission. With JIS Class 4 waterproofing, it can withstand light rain and dew without damage.