Sky-Watcher Plossl SWA 20mm 58° 1.25″ Eyepiece
Overview
The Sky-Watcher Plossl SWA 20mm eyepiece is a high-quality optical accessory designed for astronomers of all experience levels. Thanks to its wide 58° apparent field of view, it delivers a comfortable and detailed view of the night sky - including nebulae, star clusters, and planetary objects. The optical design ensures sharp, high-contrast images all the way to the edge of the field, making it especially rewarding when observing large deep-sky objects.
Optical Design
This eyepiece is built on a hybrid optical system inspired by the proven Plossl design, enhanced with modern optical elements. A 5-element, 3-group lens configuration effectively minimizes common optical aberrations such as chromatic aberration and field curvature. The result is a clean, bright, and detailed image that will satisfy both beginner and experienced observers alike.
Fully Multi-Coated (FMC) Optics
All optical surfaces of the eyepiece are treated with Fully Multi-Coated (FMC) anti-reflection coatings, which significantly reduce unwanted reflections and maximize light transmission. This is particularly beneficial when observing faint objects under dark sky conditions. The Sky-Watcher SWA 20mm eyepiece is designed to extract the maximum performance from your telescope's light-gathering capability with minimal light loss.
Eye Relief and Comfort
The eye relief of 16mm from the last optical element allows comfortable viewing even for observers who wear glasses. A rolldown rubber eyecup lets you adjust the eye distance to suit your individual needs while shielding your eye from stray ambient light. With a total weight of 174g and a compact length of 72mm, this eyepiece provides a well-balanced solution that will not strain your telescope's focuser or mount.
Compatibility and Recommended Use
The eyepiece features the standard 1.25″ barrel diameter, making it compatible with the vast majority of astronomical telescopes available on the market - from refractors and reflectors to catadioptric systems. It is well-suited for both visual planetary and lunar observation and for sweeping wide star fields and extended nebulae. The 20mm wide-angle eyepiece provides a comfortable medium magnification that makes it an ideal foundation for any eyepiece collection.
Technical Specifications
| Parameter |
Value |
| Focal Length |
20mm |
| Apparent Field of View |
58° |
| Barrel Diameter |
1.25″ |
| Optical Design |
Hybrid Plossl (SWA), 5 elements in 3 groups |
| Coatings |
Fully Multi-Coated (FMC) |
| Eye Relief |
16mm |
| Weight |
174g |
| Length |
72mm |
| Eyecup |
Rolldown rubber |
Who Is This Eyepiece For?
Beginners
The generous eye relief, wide field of view, and forgiving 20mm focal length make this eyepiece easy to use for those just starting out in astronomy. It is straightforward to locate objects and keep them in view during a session.
Intermediate and Advanced Observers
Experienced astronomers will appreciate the FMC coatings, minimal aberrations, and the versatile focal length that pairs well with both short and long focal length telescopes. It works equally well for galaxy hunting, globular cluster observation, and detailed lunar exploration.
Key Features at a Glance
- 58° apparent field of view for immersive, wide-angle views
- 5-element, 3-group hybrid Plossl optical design
- Fully Multi-Coated (FMC) optics for maximum light transmission
- 16mm eye relief - suitable for eyeglass wearers
- Standard 1.25″ barrel - universal telescope compatibility
- Rolldown rubber eyecup for adjustable comfort
- Compact and lightweight: 174g, 72mm length
- Ideal for deep-sky sweeping, planetary viewing, and lunar observation
