Celestron Omni 56mm 2" Plössl Eyepiece – A Wide-Field Low Power Giant for Deep Sky Exploration
The Celestron Omni 56mm 2" Plössl eyepiece is designed to deliver expansive low-power views, making it an excellent choice for deep-sky observing and framing large celestial objects like the Andromeda Galaxy, the Pleiades, or wide swaths of the Milky Way. With its ultra-long 56mm focal length and standard 2" barrel, this eyepiece is all about maximizing true field of view—perfect for sweeping the heavens with large-aperture telescopes.
While shorter focal length Plössls excel in planetary and lunar detail, long focal length Plössls like the 56mm Omni serve a different purpose: giving observers the largest possible field of view for visual observing or as a finder eyepiece. It's a favorite among visual astronomers who want to fully experience the scale and grandeur of the night sky, especially when used with slower focal ratio scopes like Schmidt-Cassegrains or Maksutovs.
Optics and Design
The Celestron Omni 56mm Plössl uses a classic four-element symmetrical design, known for delivering crisp, flat-field images with minimal distortion across most of the field. The optics are fully multicoated to enhance light transmission and contrast, helping faint nebulae and galaxies stand out more clearly against the dark background of space.
The 56mm focal length provides a huge exit pupil when paired with telescopes of f/10 or slower, making it well-suited to maximizing brightness in deep-sky objects. However, in faster scopes, the exit pupil can become excessively large, potentially leading to some light loss as your eye’s pupil can’t capture all the delivered light. This eyepiece performs best in scopes around f/10 to f/15, such as Celestron’s popular SCTs.
Build Quality
Celestron’s Omni eyepieces are built with durability and usability in mind. The 2" barrel is threaded for standard 2" filters, allowing you to easily attach light pollution or nebula filters for enhanced performance. The barrel is precision-machined and blackened internally to reduce reflections and stray light. A rubber grip ring around the body makes it easier to handle in the dark, even with gloves on.
The eye lens on the 56mm is large and easy to view through, and the eyepiece offers very generous eye relief—ideal for eyeglass wearers or those who prefer a more relaxed viewing experience. While the apparent field of view is a modest 47°, the true field—thanks to the long focal length—remains impressively wide.
Who Is It For?
This eyepiece is best suited for:
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Deep-sky observers who want to view large objects or scan rich star fields.
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SCT or Maksutov owners looking to wring every bit of true field from their scope.
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Astronomers who need a low-power finder eyepiece to frame targets before switching to higher magnifications.
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Eyeglass wearers who appreciate generous eye relief and comfortable viewing.
Considerations
Due to its long focal length, this eyepiece is not ideal for fast focal ratio telescopes (like f/5 Newtonians), where the exit pupil could exceed your eye’s dilation limit and reduce perceived image brightness. Also, because of its relatively narrow apparent field of view, it won’t feel as immersive as modern wide-angle eyepieces—but it excels at what it’s designed to do: offer the longest, brightest views possible through a 2" barrel.
If you’re looking for a cost-effective way to unlock the widest fields your telescope can offer, the Celestron Omni 56mm 2" Plössl delivers sharp performance and dependable build quality in a classic optical design. It’s a solid addition to any serious visual astronomer’s eyepiece kit, especially if you favor deep-sky observing with long focal length instruments.
