Pentax · Eyepiece
Pentax XW 20mm
Premium wide-field eyepiece with top-tier optics and serious eye relief for extended observing sessions
Performance Scores
Overview
The Pentax XW 20mm is a high-quality eyepiece aimed at amateur astronomers who want reliable, comfortable performance across a range of targets. With a 70-degree apparent field of view, it strikes a useful balance between wide-field sweeping and detailed planetary or deep-sky work, making it a genuinely versatile choice rather than a specialist tool. The 20mm eye relief is a real advantage for eyeglass wearers or anyone who spends long stretches at the eyepiece.
You can observe without pressing your eye against the lens, which reduces fatigue significantly during longer sessions. Optically, the XW series uses lanthanum glass elements to minimize chromatic aberration and maintain contrast across the field. Pentax's SMC multi-layer coatings push light transmission to around 96 percent at 550nm, which translates to noticeably brighter images compared to budget alternatives.
Internal baffling reduces stray light and keeps contrast high, which matters when you are hunting faint nebulae or resolving star clusters. At $419, this is a premium purchase. It is not the right call for someone just starting out, but for observers who have identified the 20mm focal length as a workhorse range for their setup, the build quality and optical performance justify the investment.
At a Glance
20mm
Focal Length
Specifications
Key Features
- 70-degree apparent field of view suits both deep-sky sweeping and planetary observation
- 20mm eye relief makes this one of the more comfortable eyepieces available for extended sessions
- Lanthanum glass elements reduce chromatic aberration and maintain edge sharpness
- SMC fully multi-coated optics deliver approximately 96 percent light transmission at 550nm
- Internal light-shielding baffles reduce reflections and improve contrast on faint targets
- Weatherproof construction holds up to outdoor use across varying conditions
- Rated 4.6 out of 5 across 117 Amazon reviews, suggesting consistent real-world satisfaction
Customer Reviews
117 reviews
Very nice eyepiece. Clear and sharp. NOTE: eye relief is not really enough for eyeglass users. I always removed my glasses to use this Pentax eyepiece.
This is probably one of my favorite eyepieces. It’s great for those not wearing eyeglasses at the eyepiece. Fantastic contrast and objects look fantastic through it.
Great optics with a moderately wide field at a lower price than some of the competition. However, for me eye placement is critical to avoid the kidney bean effect. The adjustable eye cup is helpful in getting the eye position right. I use a 5mm Nagler, bought used, for outreach, as the eye position ...