Explore Scientific 68 Degree 40mm Eyepiece Review


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Are you looking for a long focal length eyepiece?

Do you want to extend your field of view at the same time?

Explore Scientific (ES) has a 68-degree series of eyepieces that offer just that.

The 40mm eyepiece will complete your collection as the lowest power eyepiece with a wide field of view.

It is everything high-end, high-quality, and high-value.

Zooming in…

✔️ Best Feature: High-quality value

Worst Feature: Heavy

👌 Ideal For: Low Magnification, Wide FOV, Planets, DSO, Beginners, Intermediates, Experts

  • Barrel Size: 2”
  • Apparent Field of View: 68 degrees
  • Focal Length: 40mm
  • Eye Relief: 31mm
  • Field Stop Diameter: 45.5mm

Our Verdict: Explore Scientific makes superior eyepieces better than many of the popular telescope brands currently in the market. Their 68-degree 40mm is a favorite of the masses. It’s one of the finest of its kind at a cost-friendly price point that even your wallet will not disagree with.

Who is the Explore Scientific 68-degree 40mm Best Suited to?

For those looking for wide fields of view at low power, this is the eyepiece you want to own. The ES 68-degree eyepiece offers sharp and flat views and will likely be the longest focal length, low power eyepiece you’ll ever have.

This price range is best suited to intermediate and advanced users. However, beginners looking for the best performance and quality from their eyepieces from the get-go will appreciate the value of the ES eyepiece, and of course, the stunning views.

How Does the Explore Scientific 68-degree 40mm Perform?

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The 40mm eyepiece with a 68-degree AFOV is a workhorse and performer. It has excellent corrective technologies that is easily recognizable by its aberration-free views.

The view if more than fairly flat, has sharp field stops, little to no light scatter, and has excellent contrast to make out more regardless of where or what you’re looking at.

Who can use the wide-angle eyepiece? Anyone can. It has extremely forgiving eye relief that even glasses-wearers will be able to find comfort while observing.

Features & Benefits

High-Quality Value

At some point, you may end up spending twice the amount on an 100-degree eyepiece, but when you’re not ready to spend that kind of money, settle for 68-degree views and the accompanying price points. 

Settling may be a poor choice of word, because the 68-degree eyepiece is of excellent, high-end quality. It’s a fantastic eyepiece that keeps on giving – high-contrast, sharp resolution, and almost no chromatic aberration across the entire FOV.

The Explore Scientific eyepiece is incredibly comfortable to use with very forgiving eye relief and a soft eyecup. With everything it offers, it’s worth the price and will allow you to see extreme details on planets, nebulae, galaxies, you name it.


68-degrees provides a great field of view, but when you want more from a given view, it’s contrast and sharpness that you’re after, not necessarily just a super wide field of view.

The ES 68-degree eyepiece has a baffled interior with a flat, black finish. The lens elements themselves have blackened edges to help prevent light from scattering and causing internal reflections.

With increased contrast, you can make out more detail on any given object and bring to life some of the faint objects that would otherwise remain unseen.

Super Long Eye Relief

The Explore Scientific has an incredibly long 31mm of eye relief. It’s extremely forgiving, so those who wear glasses will be able to comfortably enjoy using it.

To add to comfort, the eyepiece comes with a foldable and removable soft silicone eyecup. You’ll be able to spend more time at the eyepiece and keep an object within the FOV longer before drift requires adjustments.

Waterproof and Fogproof

Yes, the ES 68-degree eyepiece is both waterproof and fogproof. The optics are O-ring sealed and with argon gas, you can remain confident that coatings will last longer, it won’t leak through a compromised seal, and it cools slower than nitrogen, so you won’t be having to deal with internal fogging ruining your night of observation. 

The eyepiece has been tested to be waterproof for 30 minutes in one meter of water. That’s an incredible time to provide resistance to this intrusive fluid. Whether you clean the lenses, drop it in a puddle, or if it was exposed to rain, you can feel confident that the optics remain untouched in their pristine condition.



For a 68-degree eyepiece, it sure is heavy weighing in at 35.2 oz. However, with the quality, 2” barrel, and long eye relief that you can get in the mix, the weight is certainly understandable. Just tally up your loads if you need to be weight conscious with your setup.

Popular Questions

What is the Warranty on the Explore Scientific 68-degree Eyepiece?

The 68-degree eyepiece is covered with a 1-year manufacturer warranty. If you register the eyepiece within 60 days of purchase, warranty coverage is converted to Explore Scientific’s Explore Star Warranty which is a limited lifetime warranty. It is fully transferable, offers free cleaning services, and is qualifiable with their trade-up program.

What is the Explore Scientific 68-degree 40mm Eyepiece Size?

The 40mm eyepiece in the 68-degree series has a 2” barrel. You will need an adapter if you have a 1.25” focuser assembly.

How does Explore Scientific Compare to Tele Vue Eyepieces?

This is a common question that is asked when one is looking to buy high-end eyepieces. Both brands offer eyepieces in the high-quality and expensive eyepiece market, but it comes down to having a preference.  

Tele Vue tends to offer very expensive eyepieces with technologies that Explore Scientific can either match or come very close to. Explore Scientific offers a better starting price on eyepieces, but Tele Vue has a reputation of having the best optical views free of aberrations.

However, the wallet usually determines what is going to be bought.


Explore Scientific eyepieces are excellent eyepieces to have. They’re expensive, but much more price friendly than its alternatives.

This particular eyepiece offers excellent wide fields of view with flat, high-contrast, and sharp views. Combine this with its fully weatherproof body, long eye relief, and soft eyecup, and the 68-degree eyepiece is lacking nothing. Whether it’s your first premium eyepiece or your 10th, this is a long-term keeper that you can explore the skies with at low power.

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The allure of the cosmos captivates Fern, with its endless wonders and celestial majesty. There’s a unique tranquility, yet an undeniable thrill, in uncovering the intricacies of our vast galaxy. Away from her telescope, Fern finds solace in the pages of a gripping novel, often accompanied by a cup of her favorite tea.