Inspired by the venerable Nagler design, the 7-element/5-group lens configuration employed in the Tele Vue Nagler Type-4 17mm Eyepiece maintains the contrast and clarity of the original design, and is optimized for deep-sky viewing.
Built to Tele Vue's exacting standards, the Type-4 features anti-reflection fully multi-coated optics to improve brightness, color rendition, and contrast. The proprietary click-stop Instadjust eyecup assures proper space between the eye and lens for eyeglass users, while blocking interfering stray peripheral light from distracting from the viewing experience for those not wearing eyeglasses. Despite its moderate focal length, the optical properties allow it to maintain an impressive 82° wide apparent field of view, and a long 17mm eye relief that provides ample space between the lens and eye to prevent accidental contact that can interfere with views. This model has a large 2" barrel diameter to make it even more comfortable to view through, and a textured rubberized grip for sure handling.