52° 30mm Waterproof EyepieceFeatures Using advanced computer design, combinations of low dispersion and high refractive index optical glasses, and durable multilayer deposition coatings, Explore Scientific 52 Series Argon Purged Waterproof eyepieces are optimized to produce high contrast, high resolution, and superior flat field characteristics. The 52 Series eyepieces are par focal (meaning they focus at near the same point regardless of the focal length you select) and come