Pentax XW 5mm 70° 1.25″ Eyepiece
A 5mm focal length combined with a 70° apparent field of view makes the Pentax XW 5mm an outstanding choice whenever detail matters - observing planets, double stars, or fine nebula structure. The image looks natural and open, with no distracting artefacts at the edge of the field of view.
Optical design
The optical system uses low-dispersion lanthanum glass, which significantly reduces chromatic aberration and minimises distortion. The design went through extensive computer simulation before production. The result is high contrast, a bright image, and very little internal reflection. Pentax SMC multi-coatings are applied to all eight optical elements, arranged in five groups. This maximises light transmission and preserves natural colour rendering.
Build quality and usability
The XW series meets the JIS Class 4 waterproof standard, so the eyepiece handles rain and high humidity without risk of damage to the optics. The solid metal barrel measures 61mm in diameter and 127mm in length - a substantial, well-built instrument. At 395g, the weight reflects the quality of construction. The 20mm eye relief allows comfortable viewing with glasses, without losing any part of the field of view.
How does it compare?
The Pentax XW 5mm eyepiece sits alongside the best products from manufacturers such as Tele Vue. In that comparison, it holds its own without reservation.
Key specifications
| Parameter |
Value |
| Focal length |
5mm |
| Apparent field of view |
70° |
| Barrel diameter |
1.25″ |
| Eye relief |
20mm |
| Optical elements |
8 elements in 5 groups |
| Coating |
Pentax SMC (fully multi-coated) |
| Glass type |
Low-dispersion lanthanum glass |
| Waterproof rating |
JIS Class 4 |
| Barrel diameter (body) |
61mm |
| Length |
127mm |
| Weight |
395g |
Who is this eyepiece for?
The Pentax XW 5mm suits observers who want the best possible view of planetary detail and fine celestial structure. It works equally well for beginners who want to invest once in a quality piece of kit, and for experienced observers who demand optical excellence in the field.
Ideal for observing
- Planets - surface detail on Jupiter, Saturn's rings, Mars
- Double stars - clean separation even at high magnification
- Nebulae - fine structural detail with strong contrast
- Observers who wear glasses - 20mm eye relief means no compromise
Why choose the Pentax XW 5mm?
- Low-dispersion lanthanum glass keeps colours accurate and edges sharp
- Pentax SMC coatings on every optical surface deliver maximum brightness
- Waterproof construction protects the optics in real outdoor conditions
- Solid metal body built to last for years of regular use
- Competes directly with the finest eyepieces available anywhere
