Explore Scientific


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Product Overview

The longest focal length in the 52° Series with the longest eye relief, the 40mm is also the only 2.0-inch O.D. eyepiece in this series. Explore Scientific now has three 40mm eyepieces in its collection, the other two are the 40mm 62° Series, and the 40mm 68° Series. At this focal length, this eyepiece is generally reserved for deep sky observers who challenge themselves to observe near the faintest observable limit of their telescopes. The huge true field of view is perfect for deep sky objects like the Andromeda Galaxy, the Rosette Nebula, as well as large star clusters, and comets.

Explore Scientific Waterproof Eyepieces - Comfort, Quality, Value. The Explore Scientific 52° Series eyepieces are excellent flat-field multi-element oculars that can transform your visual astronomy experience. With an apparent field of view of 52 degrees, these eyepieces offer incredible value in a very nice eyepiece. Expect exceptional quality, eye relief and value versus a comparably priced Plossol.

Another great benefit of these eyepieces is the excellent contrast and ease with which you can gaze, not directly at an object, but slightly to either side. This skill, called using averted vision, is especially helpful when observing faint objects, because using averted vision puts the image on a part of your eye that is more sensitive to light, allowing you to see fainter images.


Item NumberEPWP5240–01
Focal Length40mm
Weight385.5 grams; 13.6 oz.
Barrel Size/Type2.0" O.D. / Double Taper
Eye Relief27.1mm
Field Stop Diameter36.3mm
CoatingsEMD (Enhanced Multi-Layer Deposition) on all lens-to-air surfaces
Lens Elements/ Groups4 Elements in 2 Groups; Edge Blackened
Filter ThreadFits Standard 2.0-inch Dia. Thread in Filters (48mm x 0.75mm)
WaterproofO-Ring Sealed Argon Gas Purged; Tested Under 1 Meter of Water for 30 Minutes
EyecupRemovable Flip-Down Style Soft Silicone Rubber
Lens CapsSlide-on Top and Bottom
MaterialsOptical Glass; Aluminum; Steel; Silicone Rubber
MarkingsLaser Engraved: Focal Length; Series; Serial Number; Brand


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