Eyepiece PENTAX XW 7 — 20 mm focal length, black, premium wide-field optical eyepiece

PENTAX XW 7 — 20 mm focal length eyepiece is a premium wide-field optical eyepiece optimized for visual observation with telescopes and PENTAX spotting scopes. Manufactured in Japan, it combines a short focal length with a 70° apparent field of view to present a broad, immersive image. The eyepiece uses high-refraction, low-dispersion lanthanum glass to deliver bright, high-resolution views with minimal chromatic aberration and reduced distortion. Compact packaged dimensions make it convenient for field use in astronomy, birdwatching and terrestrial observing, while JIS Class 4 weather-proof construction improves reliability in challenging outdoor conditions.

Advantages

The XW 7 offers a wide apparent field of view (70°) and a short 20 mm focal length that together enable easier framing and a more immersive viewing experience. Lanthanum glass elements provide high contrast and low dispersion for clear, sharp images across the field. The eyepiece’s compact design and weather-proof construction increase portability and durability for outdoor use. Its comfortable eye relief makes extended observation sessions less fatiguing and simplifies eyepiece swapping on compatible instruments.

Suitable for

• Astronomical observations with telescopes requiring a wide-field eyepiece
• Birdwatching and wildlife observation with spotting scopes
• Terrestrial viewing where high resolution and low distortion are important
• Fieldwork that demands compact, weather-resistant optical accessories

Key specifications

• Focal length: 20 mm
• Apparent field of view: 70 degrees
• Optical glass: high-refraction, low-dispersion lanthanum glass
• Finish: black
• Packaged dimensions (approx.): 190 × 83 × 100 mm
• Weather resistance: built to JIS Class 4 standard

How to use

Install the eyepiece in the focuser or eyepiece holder of a compatible telescope or PENTAX spotting scope following the instrument manufacturer’s instructions. Adjust the focus until the image is sharp, then fine-tune the eyepiece position for comfortable eye relief and full field coverage. For best results, use with properly collimated optical systems and appropriate magnification for the observing target. Allow the eyepiece and optical instrument to reach ambient temperature before critical observations to reduce temporary focus shifts.

Usage recommendations

Handle the eyepiece by the barrel and avoid touching optical surfaces. Clean lenses only with a blower, soft brush or lens tissue and appropriate cleaning fluid when necessary. Store the eyepiece in a protective case in a dry environment to preserve coatings and mechanical parts. For observations in cold or humid conditions, allow the eyepiece to acclimate and protect the eyepiece from direct precipitation despite its weather-proof design.