Sky-Watcher Plossl SWA 2.5mm 58° 1.25″ Eyepiece
Overview
The Sky-Watcher Plossl SWA 2.5mm is a premium wide-angle eyepiece with a 58° apparent field of view, delivering exceptionally sharp images with high contrast. Thanks to its short 2.5mm focal length, this eyepiece is designed primarily for observing planets, the Moon, and other detail-rich objects at maximum magnification. The hybrid Plossl optical design ensures excellent aberration correction and uniform sharpness across the entire field of view. The eyepiece is compatible with all telescope types featuring a standard 1.25″ barrel diameter.
Optical Design
This eyepiece uses a hybrid Plossl optical scheme with 5 lenses arranged in 3 groups. All optical surfaces are treated with Fully Multi-Coated (FMC) anti-reflection coatings, which maximize light transmission and minimize unwanted reflections. The exit pupil diameter is 2.5mm, and the eye relief reaches 16mm - ensuring comfortable viewing even for eyeglass wearers. The outstanding light transmission provided by the FMC coatings is especially noticeable when observing faint objects or when working with fast focal ratio telescopes.
Build Quality and Ergonomics
The eyepiece features a standard 1.25″ barrel diameter and a maximum outer diameter of 44mm. The overall length is 93mm and the weight is 188g, giving it a solid and robust feel. The height-adjustable eye cup is twist-up and fitted with a soft rubber eyeguard that protects both the eye and eyeglass lenses, while allowing comfortable adjustment of the viewing distance.
Specifications
| Parameter |
Value |
| Focal Length |
2.5mm |
| Apparent Field of View |
58° |
| Barrel Diameter |
1.25″ |
| Optical Design |
Hybrid Plossl, 5 elements in 3 groups |
| Coating |
Fully Multi-Coated (FMC) |
| Exit Pupil |
2.5mm |
| Eye Relief |
16mm |
| Maximum Outer Diameter |
44mm |
| Overall Length |
93mm |
| Weight |
188g |
| Eye Cup |
Twist-up with soft rubber eyeguard |
Ideal Observing Targets
This eyepiece is the ideal choice for observers seeking a high-performance planetary eyepiece for maximum magnification. The short 2.5mm focal length combined with the 58° field of view allows detailed study of:
- Planetary atmospheres (Jupiter's cloud bands, Saturn's rings, Mars surface features)
- Lunar surface details - craters, mountains, and rilles
- Double stars - clean splitting at high magnification
- Globular star clusters - resolving individual stars at the edges
Telescope Compatibility
The Sky-Watcher SWA 2.5mm eyepiece works reliably with refractors, reflectors, and catadioptric telescopes. It is recommended to use this eyepiece with telescopes whose focal length allows a magnification matching the aperture diameter, in order to fully utilize the potential of this high-magnification optic. All telescopes with a standard 1.25″ focuser are directly compatible.
Why Choose the Sky-Watcher SWA 2.5mm?
- Premium FMC coatings for maximum contrast and brightness
- Wide 58° apparent field of view for a more immersive planetary experience
- 16mm eye relief - comfortable even with eyeglasses
- Robust 188g build with twist-up rubber eyecup
- Universal 1.25″ barrel fits virtually all modern telescopes
- Hybrid Plossl design ensures sharp, high-contrast images edge to edge
