Explore Scientific 28mm 68° field argon-purged waterproof 2" eyepiece


Availability: More on the way

This Explore Scientific 28mm argon-purged is a substantial 2" eyepiece that gives impressively sharp and contrasty wide field views of nebulas, compact open clusters, globular clusters, etc. with virtually any telescope that can use 2" eyepieces.
Our Product #: ES6828A
Explore Scientific Product #: EPWP6828-01
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Product Description

This new 68° 28mm Explore Scientific is a high-quality low to medium power wide field 2" 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 2" 28mm Explore Scientific is designed for the serious deep space explorer - no matter what your telescope type. The calculator in the "formula" tab above will show you just how wide the field will be with your particular telescope. For example, the 28mm Explore Scientific will give you a 0.95 degree field at 71x with the 2000mm focal length of either a big 17.5" f/4.5 Dobsonian or an 8" f/10 Schmidt-Cassegrain. That's almost two lunar diameters and is ideal for observing emission and reflection nebulas and nebula remnants.

While it's particularly well-suited for use with Dobsonians (it provides a huge 6.2mm exit pupil for rich field observing on an f/4.5 scope, close to the maximum usable), it can provide "picture window onto space" images with any telescope that can use a 2" eyepiece. With a short focal length refractor such as the TeleVue TV-85, for example, it will give you a huge 3.17° field at 21x. This eyepiece would be a welcome addition to any serious eyepiece collection.

The eye relief of this six lens/fully multicoated is an excellent 22mm. That means that this 28mm Explore Scientific can be used by most eyeglass wearers with no vignetting of the 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 2"
Eye Relief 22mm
Field of view 68
Focal Length 28mm
Number of optical elements 6
Weight 16 oz.
Warranty 1 year, extendable to lifetime


Review by:
Great low power eyepiece that is well corrected even in faster scopes (f/5). I did a head to head comparison with the Televue Panoptic 27mm, and the ES 28mm compared very favorably, offering perhaps 85% of the Panoptic's performance, but at a significantly lower price. (Posted on 10/28/2019)
Review by:
I purchased this eyepiece several years ago and it is one of my favorite EPs when using my ES127ED (7.5 focal ratio) and my 10 inch dob (5.0 focal ratio). I chose this EP because it would provide a fairly large Field of View and the cost was within my budget. I have since purchased the 30 mm 82 degree EP, however, the 68 degree EP gets used much more due to its much smaller size and much less weight. The 28mm 68 degree EP provides good contrast and is well corrected at the outer 20 percent edge, particularly in the ES127. This has been one of my best EP purchases.

I gave 4 stars but it deserves 4.5 stars. (Posted on 10/18/2019)
Review by:
I purchased this based upon the FOV for my 6"F5 Newtonian. I use it for scanning the sky to find objects or for larger views such as M31 or the moon. It is a large eyepiece, larger than I'm used to but it gives very good views that are pretty flat and no false colors on most objects. (Posted on 9/10/2019)
Review by:
I chose this eyepiece over the ES 82* 30 mm because I believed it would provide similar views at 2/3 of the cost. It also weighs about half which helps with balancing my scopes. I am very pleased with this eyepiece as it does all that I hoped for. It barlows well which makes it very versatile. I use it in my 10" f/4.7 Dob as well as my 4" f/7 refractor. It is very well made and I am sure it will provide pleasing views for many years to come. (Posted on 8/30/2019)
Review by:
I chose this eyepiece over the ES 82 degree 30 mm because I believed that it would give close to the same views at 2/3 of the cost. It is also about half the weight of the 82* 30 mm, which helps with balancing my scopes. I am very happy with my choice as it provides very bright and wide field views. I use it my 10" f/4.7 Dobsonian as well as my 4" f/7 refractor. It also barlows very well at 1.5 and 2x. It is very well made and I am sure it will provide many years of pleasant views. Overall, I am very happy with this eyepiece. (Posted on 8/30/2019)
Review by:
As the Director of Lake Afton Public Observatory (lakeafton.com), I bought this to "match" our f-13.5 main telescope (based on exit pupil) It is an outstanding eyepiece for the price! Very sharp and distortion free. We will likely buy this brand again. (Posted on 1/15/2019)
Review by:
Bought this as a "match" to our f/13.5 main telescope. (giving a 2mm exit pupil)
IT IS OUTSTANDING! Tack sharp and great contrast. It has threads for 2" (48 mm) filters.
If you "match" the focal length to double (triple?) the f-ratio of your telescope, you will "love" this eyepiece! (Posted on 1/15/2019)
Review by:
I needed a big gulp eyepiece that was not 2 or 3 pounds of metal and glass. I used to own the 27mm Pan for many years and I can say that this is at least 95% performance and half the cost. You lose just a smidgen of sharpness at the very edge of the FOV. But, you gain in more comfortable eye relief. Nicely made with great coatings. I works very well with my f/4.6 dob. Highly recommended as a lower cost alternative. (Posted on 1/13/2019)
Review by:
Having read other good reviews and comparing the price to a competitor's 27 mm two inch eyepiece (which I used to own), I purchased the ES 28/68. Great decision. This is one of those very comfortable eyepieces that has everything going for it. Good presentation, great eye relief, sharp field and a moderate weight. Unless you are willing to spend at least twice as much, the ES 28/68 is the way to go. (Posted on 1/13/2019)
Review by:
Purchased this due to the larger eye relief provided as both my children wear glasses and we enjoy observing together. The 28mm has a very comfortable view at 68* with a perfect amount of eye relief for eye glass wearers. The view "feels" more immersive than I was expecting from the 68*, although not as much as the 82* it feels more similiar to a Morpheus. Overall I am very pleased with this purchase! (Posted on 12/14/2018)
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