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These proprietary wide field eyepieces use six to eight lenses in unique four to six group designs to achieve a wide 70-degree apparent field of view. They run the full gamut of magnifications, from very low power to very high power. Each has an exceptionally long 20mm eye relief that gives fully unvignetted views for those with severe astigmatism who must wear eyeglasses while observing. Rotating the rubber-rimmed eyecup raises and lowers it to precisely customize the eyecup height to match your eyesight and eyeglass use. The chrome barrel of each eyepiece is threaded for standard light pollution and color filters. A safety groove cut into the chrome barrel engages the thumbscrew of the focuser to keep the eyepiece from falling if the thumbscrew accidentally loosens during use. All are multicoated on all air/glass surfaces, using proprietary Pentax Super Multi-Coatings (SMC). The edges of the lenses have been blackened to eliminate internal reflections for better contrast. All use high-refraction, low-dispersion lanthanum (rare earth) lenses to minimize chromatic aberrations and astigmatism. They can be used for all types of observing, with all telescope types, and are optically corrected for use with focal ratios as fast as f/4. They have good contrast and excellent center to edge sharpness, with very little ghosting. They are weatherproof to JIS Class 4 standards (which means that dew accumulation won’t cause a problem, although full submersion in a bucket of water is a no-no). Each eyepiece comes with plastic dust caps for the barrel and eye lens and a bolt-type plastic container for storage. They are protected against flaws in materials or workmanship by a lifetime warranty, a rarity in telescope equipment.