2″ 28mm Explore Scientific 68° Series Eyepiece


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Explore Scientific – Premium Eyepiece

Introducing Explore Scientific’s 28mm Eyepiece.

Using advanced computer design, combinations of low dispersion and high refractive index optical glasses, and durable multilayer deposition coatings, Explore Scientific 68° Series Argon-Purged Waterproof extreme wide field eyepieces are optimized to produce high contrast, high resolution, and superior flat field characteristics. The visual effect of these eyepieces with their long eye-relief and their 68° apparent field is truly a full-immersion experience. The 68° Series eyepieces are parfocal (meaning they focus at near the same point regardless of the focal length you select) and come with a removable and foldable soft silicone rubber eyecup for the comfort of the observer, and as experienced astronomers know, eye comfort is critical when trying to observe at the visual limits of the telescope.

Protection from the Outdoors – By making the eyepiece body Argon-purged, the waterproof eyepiece internal elements will remain as pristine as the day they were assembled.

Argon atoms are larger than that of Nitrogen and therefore they are less likely to leak or diffuse their way through the seals over the life of the eyepiece. The atomic radius of Argon is larger than Nitrogen by 0.13 angstroms and has a larger atomic volume by 11.2 cubic centimeters/molecule. Argon also has superior inertness vs Nitrogen (i.e. forming few or no chemical compounds with other elements) that prevents adverse reactions with eyepiece components and therefore extends the longevity of the internal components, and also prevents chemical reactions with other elemental contaminants that may be introduced through a weakened seal. And, finally because Argon is less conductive of heat than Nitrogen, Argon cools slower thereby buffering the effects of rapid temperature changes of the optics.

The sealed, dry environment is impervious to internal fogging and contaminants such as fungus growing in between the lens elements. Our waterproof eyepiece is easier to clean, and there is no risk of cleaning solution migrating from the top of the lens and seeping around edges to be trapped in between elements. To insure a perfect seal Explore Scientific test every eyepiece in one meter of water for 30 minutes.

Which eyepiece is for your telescope?  Use the Field of View Calculator to see what your eyepiece will give you.



  • Focal Length 28mm
  • Length 91.4mm
  • Width 61.3mm
  • Weight 16.1oz; 458g
  • Barrel Size 2.00″
  • Eye Relief 21.6mm
  • Field Stop Diameter 31.8mm


  • Super-Wide 68 degree Apparent Field Of View
  • Waterproof construction for protection against rain, dew and dust
  • Argon gas-purged eliminates internal condensation
  • Enhanced Multi-layer optical coatings for maximum contrast
  • All surfaces multicoated for maximum light transmission
  • Blackened lend edges to reduce ghosting and increase contrast
  • Long eye-relief – good for eyeglass wearers
  • Parfocal – little or no refocusing required when changing to another eyepiece from the same family
  • Foldable silicone-rubber eyecups

These eyepieces have been extensively reviewed

“Considered by many as an excellent performing ultra wide field that keeps pace with even the premium brands”  William Paolini

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Weight.5 kg
Dimensions18 × 18 × 10 cm