Explore Scientific AR 5.5mm 100° 2″ eyepiece
If you are looking for an eyepiece that will literally pull you into the universe, the Explore Scientific 100° series is exactly what you need. The Explore Scientific AR 5.5mm eyepiece with a 100° apparent field of view is one of the most impressive pieces of optics you can put into your telescope. The 100° apparent field of view creates the sensation of floating directly in space - no dark tunnel vision, just a vast, round view filled with detail. The short 5.5mm focal length makes it an ideal choice for high magnification and detailed observation of planets, the Moon, or fine nebula structures.
Optical design and coatings
Inside the eyepiece you will find 8 lens elements arranged in 6 groups - a configuration typical of modern ultra-wide-angle UWA designs. All optical surfaces are treated with multi-layer anti-reflection coatings that maximise light transmission and suppress unwanted reflections and ghosting. The result is an image with high contrast and accurate colours even when working with high-contrast objects such as planetary nebulae or the light-shadow boundary on the Moon.
The 2″ (50.8mm) barrel diameter ensures that the eyepiece makes full use of the light cone of modern wide-field telescopes, with no vignetting or darkening at the edges of the field.
Argon fill and weather resistance
The argon gas fill inside the eyepiece barrel is a feature that deserves special attention. Argon replaces air and prevents moisture from condensing on the internal optical surfaces even during sudden temperature changes - a classic problem when observing in the field at night. Combined with resistance to water (rainy nights, dew, fog), this eyepiece is built for real observing conditions, not just an ideal laboratory environment.
Comfort and practical features
- Eye relief of 12mm - a very respectable result for such an extremely wide field, allowing comfortable viewing without pressing the eye directly against the lens
- Fold-down rubber eyecup that can be adjusted for both observers without glasses and those who wear them
- Standard filter thread for quick attachment of planetary or OIII filters
- Weight: 606g, height: 181mm - a robust piece of equipment; telescope balance should be checked, especially with lighter mounts
Who is this eyepiece for?
The 5.5mm 100° ultra-wide-angle eyepiece is an ideal choice for experienced observers who want to combine high magnification with the widest possible field of view - those who do not want to choose between detail and overview. It excels in detailed exploration of the Moon and planets, where the short focal length generates high magnifications, and also when observing compact deep-sky objects such as globular clusters or planetary nebulae, where the immersive 100° field delivers a completely new experience. It is suitable for medium to large aperture telescopes, both refractors and reflectors, with a 2″ connection.
Summary
If you want to add one truly exceptional piece to your eyepiece collection - one that will regularly end up on the telescope first - this eyepiece is undoubtedly that choice. The build quality, robustness and optical performance of the Explore Scientific 100° series speak for themselves and have been proven by thousands of astronomers around the world.
Technical specifications
| Parameter |
Value |
| Focal length |
5.5mm |
| Apparent field of view |
100° |
| Barrel diameter |
2″ (50.8mm) |
| Number of lens elements |
8 elements in 6 groups |
| Eye relief |
12mm |
| Optical coatings |
Multi-layer anti-reflection |
| Internal fill |
Argon gas |
| Water resistance |
Yes |
| Filter thread |
Yes |
| Weight |
606g |
| Height |
181mm |
