Explore Scientific 17mm 92° field argon-purged waterproof 2" eyepiece


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This 2" 17mm 92° field Explore Scientific hyper-wide eyepiece provides an exceptional medium focal length immersive observing experience. 
Our Product #: ES9217
Explore Scientific Product #: EPWP9217-01

Product Description

You may be startled at the amazingly wide expanse of inky black sky that greets you when you first look into the 92° field of this Explore Scientific 17mm hyper-wide eyepiece. Observing with the 17mm Explore 92° feels more like you are in orbit above the Earth, taking a space walk, rather than looking through a telescope eyepiece. 

The Explore Scientific 2" 17mm is one of those eyepieces that can truly be described as showing you a "picture window view" of space. The visual effect of its long eye relief and 92° apparent field is truly a full-immersion experience. Your eye is relaxed, allowing you to easily use the "averted vision" technique to study faint details across its huge field of view.

With an apparent field of view that is close to the maximum possible for a hyper-wide eyepiece design, celestial objects are easier to locate with the Explore 92°. In non-driven telescopes, like Dobsonians or altazimuth mount refractors, an object stays in the field of view for a long time before you need to nudge the scope to center it again.

The 17mm 92° field Explore Scientific is O-ring sealed and argon-purged to be 100% waterproof. This prevents internal fogging in the eyepiece in cold weather; 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 lens elements.

The latest computer design programs have been used to optimize its performance. Its eight element/six group design uses low dispersion and high refractive index lenses and full multicoatings for high contrast, high resolution, and flat field images across its very wide 92° field of view. The lens edges have been blackened to improve contrast.

A 10" f/4.5 Dobsonian reflector has a full 1.37° field at 67x with this eyepiece, able to encompass all of the Pleiades in one field. Even an 8" f/10 catadioptric has a field more than one and a half lunar diameters across, able to encompass the full Moon with room to spare, the Orion Nebula, and many globular clusters, as well. You can use the calculator in the "formula" tab above to see just how wide the field will be with your particular telescope.

The long 20mm eye relief of the Explore Scientific 92° will not vignette the field of view for eyeglass wearers. The eyepiece has a soft fold-down rubber eyecup for eyeglass use and comes with dust covers for both ends of the eyepiece.

This individually serial numbered 17mm Explore Scientific 92° field eyepiece is backed by a limited one year warranty, which will be extended to an Explore Scientific transferable product 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 20mm
Field of view 92
Focal Length 17mm
Number of optical elements 8
Weight 2 lbs. 9.5 oz.
Warranty 1 year, extendable to lifetime


Review by:
I use this eyepiece in my Mewlon and my refractor. I have learned that to enjoy the immersive views of an eyepiece with a 90º or greater apparent field of view , that the eyepiece must have adequate eye relief. If it does not, then you will find yourself cramming your eye against the eyecup in order to experience the immersion of what the wide fields offer and you will be disappointed. This eyepiece provides excellent eye relief and the eye cup is just the right height and does a good job of blocking stray light. The entire field of view is comfortably available.
If you have a long focal length telescope, this is a superb eyepiece, which allows you moderate magnification to help darken the sky background without creating a cramped true field of view.
It is extremely massive and before you buy, be sure the load specifications of your focuser can manage the weight. This is because the lever arm force on your focuser when racked out may bend your focuser slightly and cause focuser sag,
I have not compared it to the Nikon 17 mm, but I did compare it to the 17.3 mm Delos on the same open star cluster on the same night, using the same telescope and the same star diagonal and searched very hard for a faint star visible in the Delos that was not visible in the ES 17 mm and I could not discern any difference in transparency. The polish is excellent.
I let a club mate try it in his telescope and he later told me how much he enjoyed using it.
Lastly, if you are a using an SCT with this eyepiece, its focal length will put you right into the center of that exit pupil window of 1.5 - 2 mm, which the distant galaxy hunters so much admire.
I will hazard a guess that this eyepiece is the flagship of the Explore Scientific eyepiece line and it shows.
(Posted on 7/9/2023)
Review by:
I use this in my 13.1 inch dob. This is my favorite eyepiece, even over my 31mm Nagler. The views are sharp and wide, and the moderate magnification is perfect for me personally. The first time I used it I was blown away with the ability to 'look around' inside the eyepiece, and the long eye relief keeps the image right there for me. (Posted on 10/18/2019)
Review by:
The 17mm 92degree ES is magnificent. I've used it in a C8, an AT106 triplet apo, and my C11Edge. In all cases the images are super sharp to the very edge of the view. Comfortable eye relief, wide usable field of view, and ideal moderate magnification in all my scopes make this the eyepiece I choose first, and often the only one I use. Buy it, you'll love it. (Posted on 9/12/2019)
Review by:
I have used the 17mm ES92 in an 80mm f/6 APO and an 8” f/10 SCT and this thing is fantastic. The 92-degree field is noticeably wider than the 82-degree field of a Nagler and the huge eye lens really sucks you into the view. The views are sharp to the edge as far as I can tell, and eye relief is good enough that I can rest my head on the rubber eyecup and see the edge with peripheral vision. I tried it with glasses and was just able to see the whole FOV with the eyecup rolled down. The only real issue with this is that it is MASSIVE...it weighs almost 3 pounds so make sure your scope and mount can handle that. The ES92 is a good deal, even better if you pick it up during a sale (when it usually goes for $399). It’s a great alternative to the 100-degree lines of eyepieces if you like or need the extra eye relief. (Posted on 8/17/2019)
Review by:
I'm currently using this Explore Scientific 17mm eyepiece with a 10" Meade LX600 SCT. The eyepiece provides a stunning and wide FOV that remains quite sharp and undistorted to the edge of the field. It serves as a superb complement to my 31mm Televue Nagler.

As noted in other reviews, beware of its weight. Save for this caveat, I have no hesitation whatsoever in recommending this extremely high quality eyepiece. (Posted on 7/29/2019)
Review by:
I have used this lens on a 16" Dob, a 9.25" SCT, and a 120mm Refractor. This lens never disappoints and its a great pleasure to look through. Sharp across the field (I use mine with the ES comma corrector). The only negative thing I can say about this eyepiece is that it is heavy for eyepieces (its a monster lol). You may need some counter weights if you are using it with a dobsonian to make sure it doesnt make the scope dive. I've looked through this eyepiece and compared it to my older 14mm meade Ultra Wide (Japan 80s). The 17mm is much easier to look through.
(Posted on 12/26/2018)
Review by:
I needed a wide angle in this focal length and wanted to give this a try since I had heard so many great things about it. The optics in this are absolutely world class. I have several Tele Vue eyepieces ranging from Plossls to Ethoi, and this eyepiece delivers the same caliber views as any of my TVs in both my F/5 dob and F/10 SCT. It is TACK sharp, and has transmission that is hard to beat.

The long eye relief is useful, but if you're not wearing eye glasses, you will want to flip the eyecup up for easier eye placement. The long eye relief and large eye lens can make the exit pupil a bit easy to lose (but not as egregiously as other eyepieces I've tried).

The main issue is the weight. But if you have a beefy focuser and a well-balanced scope, then don't hesitate to chuck this eyepiece in the focuser. The views are totally worth it. (Posted on 11/22/2018)
Review by:
I did get the chance to the both the 17mm and 12mm in my 11" SCT and I found the ES 92° LE eyepieces to be some of the best eyepieces Explore Scientific has ever made. At 20mm they have long eye relief, enough that you can were glasses with no problem while observing. At 92° AFOV they have a nice wide view. No blackouts, kidney beaning or any distortions all the way out to the edge. This has become my favorite eyepiece. But beware, at 2.8lbs / 1270gms it is a heavy eyepiece and this could be an issue for some people. I could only afford to buy one and decided on the 17mm, but the 12mm will be my best purchase. (Posted on 10/10/2018)
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