Explore Scientific 20mm 68° field argon-purged waterproof 1.25" eyepiece


Availability: More on the way

This Explore Scientific 20mm argon-purged waterproof eyepiece is a fine medium power 1.25" eyepiece whose substantial 68° field of view gives you "big picture" deep space performance with virtually any telescope type.
Our Product #: ES6820A
Explore Scientific Product #: EPWP6820-01

Product Description

This new 68° 20mm Explore Scientific is an excellent medium power wide field eyepiece with an unusual benefit. It is O-ring sealed and argon-purged to be 100% waterproof. This prevents internal fogging in the eyepiece; keeps the interior dust-and fungus-free; and makes it easier to clean, as there is no risk of excess cleaning solution getting trapped between the lenses.

Many observers feel that a 68° field eyepiece like this Explore Scientific hits the "sweet spot" between the affordable, but "looking down a tube" view of conventional 45°-50° field eyepieces, and the full-immersion, but very expensive, observing experience of an ultra-wide field 82° or 100° eyepiece.

The 20mm 68° Explore Scientific works with any telescope from a fast focal ratio reflector to a long focal length refractor. It provides a substantial 1.19° field of view (almost two and a half times the diameter of the full Moon) and a bright 3.64mm exit pupil with a 10" f/4.5 Dobsonian at 57x. This gives you about four minutes and forty-five seconds with such a scope to observe an object as it drifts from one side of the eyepiece's flat field to the other. That's plenty of time for multiple observers to look at the object or for you to absorb as much detail as possible before having to reposition your scope. You can use the calculator in the "formula" tabe above to see just how wide the field will be with your particular scope.

The eye relief of this six lens/fully multicoated optical system is a respectable 15mm, so observers who must wear eyeglasses when observing will see an almost unvignetted field of view. The eyepiece has a soft fold-down rubber eyecup and comes with dust covers for both ends of the eyepiece.

This individually serial numbered Explore Scientific eyepiece is backed by a limited one year warranty, which will be extended to an Explore Scientific transferable lifetime limited warranty when its warranty card is registered with Explore Scientific within 60 days of purchase. Here's a link to the full details on this unique transferable lifetime warranty.

Tech Details

Barrel Size 1.25"
Eye Relief 15mm
Field of view 68
Focal Length 20mm
Number of optical elements 6
Weight 8.8 oz
Warranty 1 year, extendable to lifetime


Review by:
Like this eyepiece but since getting the nagler 13mm dont use that much nymore (Posted on 10/17/2019)
Review by:
The 20mm 68 degree eyepiece is wonderful to gaze through in my f8 reflector. A quality build with many great attributes at this price point made this eyepiece a welcome companion to my collection. (Posted on 10/17/2019)
Review by:
I have used all the ES68's except the 40mm. My favorite is the 20mm ES68. It is extremely comfortable to use. The eye relief is borderline enough for use with eyeglasses depending upon your eyeglasses design, but it is probably better if you don't need glasses. This eyepiece has very good edge performance in the refractors I've used it in that are f/7 and longer. It provides bright images of nebulous deeps sky objects and very sharp views of the Moon. This eyepiece works very well with a barlow so you can use it at multiple focal lengths if you have quality barlows. The only area where it may come up just a little short compared to "premium" priced eyepieces is a touch more scattered light. However, for the price it is definitely a 5 star eyepiece appropriate for all observing targets that I was happy using for years. (Posted on 7/25/2019)
Review by:
I was on the lookout for a really nice eyepiece set...and the prices were depressing until I came across the Explore Scientific eyepieces. I've started with getting the 68 degree field argon purged set and then I will move to the 100 degree field higher powered set that will complete my set. When I got my first eyepiece I was and am so blown away by the quality of them. So nice and I can see this set (when completed) being with me for a very long time...even through a few telescopes. I will take them to star parties to use with other scopes. You won't be disappointed when you purchase one or more of these babies. (Posted on 7/24/2019)
Review by:
Little brother of the 24 mm/68 ES, it complements that eyepiece very well! Increased magnification in any telescope with a darker sky background. Eye relief friendly if you do not wear glasses while observing. Well mannered in the way of aberration control. no regrets with this one! (Posted on 1/13/2019)
Review by:
This is perhaps my favorite EP of all time. Clear, sharp and wide. Very comfortable EP to use - great eye relief with no blackouts. I use it with my F7 SV102 Access, by F6 AT66ED and my old discovery F5.6 ST90 - works well with all of them! Highly recommended for a reasonably priced, premium EP. (Posted on 11/16/2018)
Review by:
Along with the 6 millimeter eyepiece and a Barlow, these are a couple of my favorite ES eyepieces. Comfortable eye relief and a good field of view. (Posted on 11/11/2018)
Review by:
This eyepiece has the most comfortable amount of eye relief, and was my favorite eyepiece when used in my Sky Watcher 100ED f/9. I believe this eyepiece is somewhat sensitive to field curvature, because when I upgraded to a Sky Watcher 120ED f/7.5, the field curvature became apparent. Interestingly, the near focal length ES68 24mm eyepiece didn't have this problem. (Posted on 10/31/2018)
Review by:
I use one of these for my finder eyepiece in an 8" f/6 dob and it works great. Sharp and not too heavy. (Posted on 10/6/2018)
Review by:
I had a pair of these to use in a Bino viewer. They were great for that and paired perfectly with the small prisms in the less expensive Bono’s.

Eye relief is on the short side for glasses especially when trying to Binoview. (Posted on 10/6/2018)
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