Designed with a fully multicoated 5-element/4-group lens configuration, the Celestron Ultima Edge 10mm Flat Field Eyepiece produces bright and clear views with crisp and sharp resolution across the wide 60° field of view—even at the extreme edges. The eyepiece's focal length produces a high magnification for making detailed observations of the lunar surface, planets, or narrow areas of the night sky. This Ultima Edge has a 1.25" barrel that makes it compatible with popular diagonals, Barlows, and visual backs with standard threads for filters. It is parfocal with the 15mm and 18mm models in the Ultima Edge series, requiring little or no refocusing when changing between them. A textured collar makes inserting and removing the eyepiece easy, and the combination of comfortable 16mm eye relief and fold-down rubber eyecup makes it easy to use with or without eyewear.