Explore Scientific 52° Series 2" 40mm Waterproof Eyepiece

The 52° Series 40mm is the widest-field eyepiece in the 52° Series, using a 2" barrel to frame expansive views of large deep-sky objects. It has argon-purged waterproof construction and EMD coatings.

Key Features

• 2" barrel carries a 36.3mm field stop, the largest in the 52° Series. It is stainless steel, tapered for a more secure hold.
• Argon-purged waterproof housing, sealed against moisture and fog. O-ring seals keep dirt, fungus and cleaning fluid from getting between the lenses.
• Enhanced Multi-Layer Deposition (EMD) coatings on all air-to-glass surfaces for high-contrast images at low magnification. The patented coating also suppresses reflections and ghosting.
• 4-element, 2-group optical design with edge-blackened elements to suppress stray light across the wide field
• Fold-down silicone rubber eyecup with comfortable eye relief for relaxed viewing, including with eyeglasses. Its 27.1 mm of eye relief is the longest in the 52° Series.
• Parfocal series. All 52° Series eyepieces focus at about the same point, so swaps need little refocusing.

Ideal For

• Wide-field deep-sky observers framing large targets like the Andromeda Galaxy
• Comets and large star clusters in a huge true field
• Faint-limit observing near the faintest objects a telescope can show
• Telescope owners with 2" focusers

Accessories & Compatibility

• ED127 (952 mm, f/7.5). In the ED127 triplet, in its 2" diagonal, the 40mm gives 24x, a 5.3 mm exit pupil and a 2.2° true field.
• ED152 (1216 mm, f/8). In the ED152 triplet, also in its 2" diagonal, it gives 30x, a 5.0 mm exit pupil and a 1.7° true field.