Ricoh/Pentax Pentax Eyepiece SMC XW 23

Pentax Eyepiece SMC XW 23 – 85° apparent field of view (largest in XW series) with 20 mm eye relief

The Pentax SMC XW 23 eyepiece delivers a very wide apparent field of view of 85°. With 20 mm of eye relief, it provides comfortable viewing and a broad visual window that is especially suitable for observing nebulae and star clusters.

Wide field and viewing comfort

The combination of an 85° apparent field of view and 20 mm eye relief produces an expansive, immersive view. As a result, observers can see large celestial objects and dense star fields more naturally. This eyepiece emphasizes comfortable observation over extended sessions.

Advanced optical design for sharp edge-to-edge images

Pentax designed the XW 23 with a new optical system of 7 elements in 5 groups. This design surpasses the conventional XW series and delivers sharp star images right to the edge of the field of view. Therefore, you get consistent sharpness across the entire image circle.

The high-performance optics include lanthanum glass elements. These elements offer high refractive power and particularly low dispersion, which produces a balanced image with minimal aberrations. The design also reduces the blackout effect by effectively compensating for the spherical aberration of the pupil.

Coatings and light transmission

All lens surfaces that meet air receive the original multi-coating to maximize transmission and minimize reflections. In addition, all laminated surfaces receive an innovative partial coating. Together these treatments achieve light transmission of more than 90 percent across the visible spectrum, with an especially high 96 percent at 550 nm. The result is brighter, clearer views with improved detail.

Light-shielding for higher contrast

Pentax applied advanced computer simulation technology to position a light-shielding diaphragm in the most effective location inside the eyepiece. This reduces internal reflections and helps produce a brighter image with improved contrast, which enhances the visibility of faint structures in deep-sky objects.

Durability and weather resistance

The eyepiece features weather-resistant construction rated to JIS Class 4. You can use it in a wide range of weather conditions for reliable performance. Note, however, that it is not designed for use underwater.

Key features

• Apparent field of view of 85°, the widest viewing angle in the XW series, suitable for observing nebulae and star clusters.
• A new optical system with 7 elements in 5 groups that surpasses the conventional XW series to obtain sharp star images all the way to the edge of the field of view.
• Original multilayer coating for outstanding light transmission efficiency.
• Advanced light-shielding technology for improved image contrast.
• Weather-resistant (JIS Class 4) construction for all-weather viewing (note cannot be used under water).

Specifications

FAQ

Question: What makes the XW 23 suitable for deep-sky observing?
Answer: Its 85° apparent field of view and 20 mm eye relief give a wide, comfortable view ideal for nebulae and star clusters, while the optical design keeps stars sharp to the edge.

Question: How does the eyepiece handle stray light and contrast?
Answer: Pentax uses a light-shielding diaphragm positioned via computer simulation to reduce internal reflections, which improves image brightness and contrast for clearer views of faint details.

Question: How effective are the coatings and transmission?
Answer: All air-contact surfaces have original multi-coating and laminated surfaces have partial coating, achieving over 90% transmission across visible wavelengths and 96% at 550 nm for bright, efficient light delivery.

Question: Can I use the eyepiece in wet conditions or underwater?
Answer: The eyepiece is weather-resistant to JIS Class 4 and suitable for use in many outdoor conditions, but it is not designed for underwater use.

Question: What optical elements improve image quality?
Answer: The eyepiece uses lanthanum glass elements with high refractive power and low dispersion to reduce aberrations and balance the image, helping to minimize blackout effects and maintain sharpness.