Celestron Ultima Edge 18mm 1.25" Eyepiece
If you're looking for an eyepiece that delivers flat-field performance without breaking the bank, the Celestron Ultima Edge 18mm 1.25" should be on your shortlist. Designed with modern optical engineering and premium coatings, this eyepiece gives you pinpoint stars across the field, high contrast views, and excellent edge-to-edge sharpness—ideal for both planetary and deep-sky observing.
The 18mm focal length is a versatile sweet spot, providing medium magnification in most telescopes. In an 8" f/10 SCT, for example, you'll get about 111x—just enough power to pick apart globular clusters or bring out detail in galaxies, while maintaining a wide enough field of view for framing objects cleanly. Pair it with a 2x Barlow for an effective 9mm focal length, and you'll be set for lunar detail or double star work.
Flat-Field Performance Across the Board
The Ultima Edge series is Celestron’s answer to the demands of today’s wider-field fast telescopes. This 18mm model features an 8-element, 5-group design engineered to minimize field curvature, chromatic aberration, and astigmatism. What that means in the field: stars stay pinpoint across nearly the entire 65° apparent field of view—even in faster instruments like f/5 Newtonians or f/6 refractors.
ED Glass for Enhanced Clarity
Celestron didn’t skimp on glass. The Ultima Edge line incorporates extra-low dispersion (ED) elements to keep contrast high and color fringing low. You'll notice cleaner planetary edges, better color correction on bright stars, and a more natural tonal balance when observing open clusters or the Moon.
Premium Coatings and Construction
All air-to-glass surfaces are fully multi-coated with Celestron’s proprietary optical coatings, maximizing light transmission and minimizing internal reflections. The blackened lens edges further suppress stray light and boost contrast—especially helpful when observing faint galaxies or nebulae from darker skies.
The anodized aluminum barrel is threaded for standard 1.25" filters and features a precision-machined safety undercut to prevent accidental drops when changing eyepieces. A fold-down rubber eyecup offers a comfortable viewing experience for both glasses wearers and those observing without corrective lenses.
Comfortable Eye Relief and Usability
The 18mm Ultima Edge gives you a generous 20mm of eye relief, making it an excellent choice for eyeglass wearers. The wide, immersive 65° apparent field is easy to take in, with none of the "blackout" effect that sometimes plagues wide-angle designs with shorter eye relief. It’s a comfortable eyepiece to use for extended observing sessions, whether you're scanning the Milky Way or doing outreach at a star party.
Great for Visual Use, Planetary Imaging, and Binoviewers
Because of its flat field and low distortion, the Ultima Edge 18mm is also a solid choice for planetary imaging with eyepiece projection setups. Its relatively compact size and high-quality optics also make it a good match for use in binoviewers, delivering sharp, matched views for solar, lunar, and planetary work.
Whether you're upgrading from entry-level Plössls or building out a mid-to-high-end eyepiece collection, the Celestron Ultima Edge 18mm is a strong performer that punches above its price point. With its optical clarity, flat field, and thoughtful ergonomics, it’s a reliable all-rounder that belongs in your eyepiece case.
