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Celestron Ultima Duo 21mm Eyepiece 93445



21mm eyepiece - 1.25" and 2"

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Data sheet

Focal length 21mm
Lens elements 8 (5 groups)
Eye relief: 20mm
Field of view: 68 degree apparent FOV
Glass type Fully multi-coated
Tube diameter: 1.25 inch, 2 inch
Lens coatings: Fully multi-coated

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Celestron Ultima Duo 21mm Eyepiece

Celestron Ultima Duo eyepieces are top of the line eyepieces designed for both imaging and observation. Compatible with both 1.25" and 2" focusers, the Ultima Duo offers a wide 68 degree apparent field of view. Blackened lens edges combat internal reflection, and eight high quality lens elements produce crisp, clear views with minimal chromatic aberration.

Made from anodized aluminum, the Celestron Ultima Duo family of eyepieces include features such as a fold-down rubber eye guard (for observers with glasses), as well as integrated 42mm T-threads under the eye guard for a direct fit to DSLR cameras (with the correct T-ring, of course). The bottom of each Ultima Duo eyepiece is threaded to accept filters.

With the addition of a T-to-C adapter, Celestron Ultima Duo eyepieces are also compatible with a number of high-end imaging devices, such as Celestron Skyris and NexImage Burst cameras.

To learn more about telescope eyepieces, check out our Telescope Eyepiece Guide.


  • High performance photo-visual eyepieces quickly switch between observing and imaging
  • Fully multi-coated optics with 8 elements in 5 groups for the best correction of chromatic aberration and field curvature
  • Extra wide 68-degree apparent field of view
  • Full 20 mm of eye relief
  • Integral 42 mm T-adapter threads and threaded barrel for filters

Get a new perspective on the Universe with Ultima Duo, Celestron's versatile new eyepieces that combine excellent optics with a built-in T-adapter for astroimaging.

Enjoy impressive views with a wide 68-degree apparent field of view. Celestron’s fully multi-coated optics increase light transmission and contrast, while blackened lens edges prevent internal reflections. The result is bright, pinpoint stars on a black field. A generous 20mm of eye relief and fold-down rubber eyeguard make Ultima Duo comfortable to use without removing eyeglasses.

Perfect for Imaging

If you’re interested in imaging through the eyepiece, Ultima Duo makes the process quick and easy. Unlike competitors’ eyepieces, you won’t need to spend money on expensive adapters for your camera. The industry-standard 42 mm T-threads are integrated for a direct, secure connection to your DSLR or astronomical CCD camera. Just remove the rubber eyeguard to expose Ultima Duo’s integral T-threads. Then attach your DSLR camera (with compatible T-ring) and you’re ready to capture crystal clear images! Ultima Duo is ideal for imaging bright solar system objects like the rings of Saturn, craters on the Moon, and Jupiter’s Great Red Spot.

Imaging the Moon and planets is even easier with our Smartphone Adapter for Ultima Duo. Unlike “universal” adapters, the Celestron Smartphone Adapter is custom-fit for the Ultima Duo eyepiece line. With this sturdy connection, your smartphone can capture crisp, sharp images of your favorite solar system objects.

Advanced planetary imagers can attach Celestron’s T-to-C Adapter and add a number of high-end imagers to Ultima Duo, including our Skyris and NexImage Burst cameras.

Smart Design

Ultima Duo’s anodized aluminum body allows it to fit both 1.25” and 2” focusers, so you can use it with almost any telescope with no extra adapters required. A compact body style makes Ultima Duo an excellent choice for use with binoviewers.

The rubber grip rings provide good ergonomics so you can hold onto your eyepiece, even while wearing gloves. The aluminum barrel is threaded to accept 1.25” eyepiece filters and has a safety recess to prevent it from slipping out of the focuser. Each Ultima Duo eyepiece includes cover caps and a protective carry pouch.

Celestron Ultima Duo eyepieces are available in 6 focal lengths:

  • 5 mm
  • 8 mm
  • 10 mm
  • 13 mm
  • 17 mm
  • 21 mm


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Celestron Ultima Duo 21mm Eyepiece 93445

Celestron Ultima Duo 21mm Eyepiece 93445

21mm eyepiece - 1.25" and 2"

Write a review