This review will be about my firsthand experience with the Explore Scientific 8.8 mm and 6.7 mm 82-degree eyepieces. I will outline why I purchased them, the scopes they are used in and discuss the calculations used to determine the magnification and field of view they produce.
These are wide view eyepieces. They offer an 82-degree apparent field of view, which is where the name is derived.
While there are no standards as to what constitutes wide, the industry seems to consider anything wider than a Plossl’s 52 degrees AFOV as wide. Eyepieces with a 60 degree AFOV are considered wide. Eyepieces wider than 68 degrees seem to be considered super wide. And the term I have seen used for eyepieces wider than 80 degrees AFOV is ultra-wide. Note that there are eyepieces that go all the way to 120 degrees AFOV.
So these Explore Scientific 82 degree eyepieces would be considered ultra-wide eyepieces. Use whatever term you like, these are nice eyepieces.
Basic Features - 8.8 mm eyepiece
6.7 mm Eyepiece Features
The ES 82 eyepieces are waterproof and purged with Argon gas to prevent intrusion by moisture which could produce fogging or the internal growth of mold and fungus. While there is no reason to have eyepieces out in the rain, if you are observing in a location were heavy dew is experienced, waterproof eyepieces are a good idea.
The eyepieces are fully multicoated with Explore Scientific’s EMD coatings. Explore scientific does not provide precise information on their web site, but other sources say these eyepieces contain 7 lens elements made up of a combination of crown, flint and lanthanum glass.
They have a fold down eye cup which help you position your eye properly on the eyepiece. This can also help block stray light, which is helpful for me in my light polluted location.
They include a tapered safety barrel to resist accidental escape from your focuser or diagonal. And the eyepieces are threaded for standard 1.25” filters.
Explore scientific backs their eyepieces with a one year warranty, but read on. Each eyepiece has a laser etched serial number. If you register the eyepiece with Explore Scientific within 60 days of purchase, they convert this to their Explore Star transferrable extended life of the product warranty. Clearly, they have a lot of confidence in their products.
Let’s Discuss the View
I had been using Meade 26 mm, 9.6 mm, and 6.4 mm Plossl eyepieces in my Meade ETX 80 F5 refractor. I had also been using the Orion 25 mm and 10 mm Plossl eyepieces that came with my Orion SkyQuest XT8 Intelliscope, an F5.9 203 mm Newtonian/Dobsonian telescope.
I had no complaints about the image quality with the Plossls. Plossl eyepieces offer good sharp images in these scopes, but their apparent field of view is only 52 degrees. I was interested in a wider field of view, especially for my manually tracked XT8i.
If you combine the AFOV specification of an eyepiece with the magnification provided by the eyepiece in a given scope you can get an estimate of what the true field of view will be as you look through the telescope.
- Focal Length Scope / Focal Length Eyepiece = Magnification
Using the following simplified formula we can estimate the true field of view the eyepiece will provide in any given telescope.
- Apparent Field of View (AFOV) Eyepiece / Magnification Eyepiece = True Field of View
Using my Orion XT8, 1200 mm FL, as an example.
An 8.8 mm Plossl eyepiece with a 52 degree AFOV would produce 136X and a .38 degree true field of view. That is a little less than the width of the full moon, which is about .5 degrees.
The 8.8 mm Explore Scientific 82 degree eyepiece would produce the same 136X but you would have a .6 degree field of view, or wider than a full Moon.
The 6.7 mm ES 82 would produce 179X with a true field of view of about .46 degrees. If I used a Plossl of the same focal length, the true field of view would be a tight .29 degrees true field of view.
The wider field of view has three benefits.
- When using a manual scope, you have more drift time for the target to remain in view.
- You can see more of larger targets, such as the Andromeda Galaxy, which is over 3 degrees wide.
- You can see smaller targets in the context of their surroundings, what some people call a more immersive visual experience
The ES 82s retail for $160 each. Are they worth it? I say yes!
There are less expensive super and ultra-wide eyepieces on the market. I have tried a few. Unfortunately, when used in shorter focal ratio telescopes, say less than F7, many of the cheaper wide field eyepieces show significant distortion or aberration as you approach the edge of the field of view. However, with the Explore Scientific 82 degree eyepieces, I saw none of this in my F5 and F5.9 scopes. The images were clean, crisp and sharp.
I have also used these in my F15 Meade ETX 125 which is a Maksutov-Cassegrain design. The image is excellent. And the wide field really works well with this scope. Highly recommended for high focal ratio scopes too.
Another benefit of these eyepieces, as compared to Plossl eyepiecess and many other eyepiece designs is eye relief. This is the distance you should have your eye from the lens in order to see the entire field of view.
A typical 9 mm Plossl eyepiece would have about 6 mm of eye relief. That would mean you would have to have your eye almost touching the lens in order to see the full field of view. Compare this to the 15.6 mm of eye relief for the ES 82 8.8 and you will see why the ES 82 is much more comfortable to use.
A 6 mm Plossl has a super short 5 mm of eye relief as compared to the 15.7 mm of eye relief for the ES 6.7 82 degree eyepiece. And of course, that full field of view is much smaller in the Plossl.
If you are an eyeglass wearer, eye relief is critical. You can’t get your eye within 5 mm of the top lens of an eyepiece with your glasses on. So you need that extra eye relief in order to see the field of view.
I wear glasses, but not when I observe. With 15.6 mm and 15.7 mm of eye relief, respectively, without my glasses, I find these very comfortable to use. However, I have tested these with my glasses. I am able to see the full field of view with my glasses.
What's The Bottom Line?
The ES 82 are excellent eyepieces and well worth the price because:
- They provide a much wider field of view than the standard Plossl
- They provide a much longer eye relief making them more comfortable to use and more suited to eyeglass wearers
- They are better corrected for use in lower focal ratio scopes than many less expensive wide view eyepieces
To summarise this Explore scientific 82-degree line review, I highly recommend it. And I plan to continue to build out my set over time.