| TeleVue Radian eyepieces have six or seven lens elements, depending on the focal length. The Radians are designed for medium to high power use down to f/4 with any type of telescope. They use multiple rare earth elements for superb lunar and planetary contrast, a rarity among wide field eyepieces with as many elements as these have. Other advantages of the multiple rare earth element design include a consistent and very long 20mm eye relief, plus a consistent and quite wide 60 degree field of view for outstanding high power views of the Moon, planets, globular clusters, and compact planetary nebulas. The field is very flat, producing sharp images from edge to edge. The Radians are designed to combine high power with long eye relief, usually mutually exclusive terms, for those observers who need eyeglasses to correct for astigmatism. The fact that they provide an exceptional viewing experience for all observers, perfect eyesight or not, should not come as a surprise to anyone who has ever looked through a TeleVue eyepiece. Each is fully multicoated, with blackened lens edges for high contrast. All Radian eyepieces are parfocal with each other. A soft rubber grip ring on each provides a more comfortable and secure hold in cold weather. They are threaded for standard 1.25 filters. TeleVue's unique "Instadjust" click-stop adjustable-height eyeguard gives a full 20mm of eye relief with the eyeguard retracted all the way, an exceptional amount at any focal length, and outstanding in the shorter focal lengths. The eyeguard can be raised in small and repeatable increments to position the eye of the non-eyeglass wearer the precise distance from the eyepiece to see the full field of view. A soft fold-down rubber eyecup helps eliminate contrast-reducing ambient stray light. A special doughnut-shaped removable plastic insert fits into the eyeguard to center the eye for those who have trouble positioning their eye precisely on a small exit pupil. These are exceptional eyepieces for the truly discriminating observer.
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