Explore Scientific 120 2" 9mm Eyepiece

Explore Scientific 120 2'' 9mm Eyepiece


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Model:  es_120_9mm
Part Number:  0218909
Brand:  Explore Scientific

Explore Scientific

"The outstanding views this eyepiece delivers mark it out from the crowd. Constructed from 12 lens elements arranged in eight groups, the eyepiece offers such a wide apparent field of view that your eye can really relax into it – it’s a pleasure to use. In addition, the medium-power magnification granted by its 9mm focal length still allows you to get in close to your target.

When using it to observe the vast Andromeda Galaxy, M31, through a 4-inch refractor, the view feels like one you’d get using a low-power eyepiece with a much larger scope. One hidden advantage of being able to look around the field of view is that it’s also easier to use the averted vision technique, looking to the side of an object to place its delicate light on a more sensitive part of your retina.

Each lens element is multicoated with blackened edges. This results in an exquisite high-contrast view that really is a joy. It’s truly an amazing experience using this eyepiece."  BBC Sky @ Night magazine review


Observing the night sky with this eyepiece it is easy to forget you are looking through a telescope. It must surely be the nearest we can get to actually ‘being there’. 

Other than it’s larger size and phenomenal FOV (Uber-Wide?) Explore Scientific’s 120° eyepiece is essentially the same as their 100° models. Which is good because optically and mechanically they are very impressive. 

A good choice for use with all telescopes with ratios f5 and higher but it is an especially good choice for Dobsonians because the huge FOV makes targets easier to locate and, for owners of non-driven telescopes, the target stays in the FOV for a long time before the telescope needs repointing. 

The hyper-wide FOV also makes it easier to observe using ‘averted vision’ which involves not looking directly at the object, but looking a little off to the side, while continuing to concentrate on the object. Doing this projects the object onto a part of your eye that is more sensitive to light. This technique is most useful when observing large faint nebulae and star clusters. 

Exotic glass lenses (12 lens elements in 8 groups) fabricated from combinations of Dense Crown, Light Crown, Dense Flint and Lanthanum with multiple anti-reflection coating on all air-to-glass surfaces ensures bright high contrast views. Blackened lens edges and internal baffling also enhance contrast and minimise ghosting from internal reflections. 

Sealed waterproof construction and an Argon gas-purged interior protect the eyepiece from rain or dew and and eliminates internal condensation to ensure the optics remain pristine.

Foldable rubber eyecup and long eye-relief make them a good choice for use with eyeglasses and a tapered nosepiece provides peace of mind because the eyepiece is less likely to fall out of the focuser if the lock-screw loosens. 

Threaded for 2” filters. 


  • Gigantic 120 degree Apparent Field Of View
  • Premium grade optical glass
  • Argon-Purged Waterproof eyepiece is internally sealed and purged with inert, dry argon gas to prevent internal fogging, to halt the intrusion of fine particulates and fungus.
  • All surfaces fully multicoated for maximum light transmission
  • Lens edges and all internal metal surface are blackened to maximise image contrast
  • Foldable rubber eyecups

Eyepiece Field of View Simulator

Product Specifications

Product Code0218909
Eye Relief12.6mm
Field Stop Diameter21.7mm
Barrel Size2 / 50.8mm
Barrel Length36mm
Lens Groups8
Height (From end of barrel)149.2mm

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June 2018 / View Older
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