Eyepiece Skywatcher SW-5401 10mm Inverting Image, 10 mm focal length

The Skywatcher SW-5401 10mm eyepiece delivers an inverting image with a 10 mm focal length designed for use with compatible refractor and reflector telescopes. This compact eyepiece increases magnification compared with standard low-power oculars, making fine details on the Moon and planets more accessible to visual observers. Its simple optical layout focuses on delivering a clear, high-magnification view where image inversion does not affect observational goals such as planetary detail, lunar surface study, and close double-star separation.

Advantages

This eyepiece offers higher angular magnification due to its 10 mm focal length, enabling improved resolution of small surface features on bright solar system objects. The inverting image design is optically straightforward and typically lighter and more compact than erecting eyepieces, which makes the SW-5401 convenient for portable setups and quick field use. Its construction is intended to provide consistent focal placement and stable eye relief for visual observation at medium-to-high magnifications.

Suitable for

• Planetary observing (Mars, Jupiter, Saturn) where higher magnification is required
• Lunar surface observation and crater detail studies
• Visual double-star splitting and high-resolution backyard astronomy
• Portable telescope setups and observing sessions where compact eyepieces are preferred

Key specifications

• Focal length: 10 mm
• Image orientation: inverting (rotated or upside-down view)
• Intended use: visual astronomy with compatible telescopes
• Form factor: compact eyepiece suitable for higher magnification

How to use

Insert the eyepiece into the telescope’s focuser or diagonal and secure it according to the telescope’s fastening method. When observing, start with a low-power eyepiece to locate and center the object, then switch to the 10 mm eyepiece to increase magnification and resolve finer detail. Because the eyepiece produces an inverting image, orientational references such as star charts should be adapted or used alongside erecting optics if an upright view is required. Adjust the telescope focus and observer eye position to obtain a sharp image and comfortable eye relief.

Recommendations

Use the eyepiece on nights of steady seeing for best results at high magnification; allow the telescope to reach thermal equilibrium and avoid excessive atmospheric turbulence. Combine with appropriate barlow lenses or diagonals only if optical compatibility and backfocus permit; using a Barlow will change effective focal length and magnification. For daytime terrestrial viewing where an upright image is necessary, choose an erecting eyepiece or use an image-erecting accessory.