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John

Explore Scientific 17mm 92 Degree Growing Enthusiasm

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I've got the 12 inch dob out tonight and the Explore Scientific 17mm 92 degree eyepiece in the focuser. To start with, when I first used it a few months ago, I was not sure that I liked the ES 17 / 92 hyperwide eyepiece but it has gradually grown on me. The optical performance is really excellent and can't be faulted. Really sharp right across the massive field of view. Stars pinpoints right at the edge in my F/5.3 dobsonian.

What has taken a little getting used to is the eye positioning which is not quite the same as my Ethos eyepieces. The eye relief is longer and this is one hyperwide eyepiece that those who wear glasses have some chance of seeing the full field of view with. As a non-glasses wearer I've had to get used to an eye position that is a little further out than I'm used to but I've gradually found a method that works and it's starting to feel more natural.

The views are stunning with this scope / eyepiece combination. The true field of view is just a touch less than 1 degree at 93.5x magnification. The views this evening of the double cluster and the Andromeda galaxy group (M31, M32 and M110) have been really impressive and very immersive. Really like looking out of the porthole of a spaceship :grin:

It's a large and heavy beast but the Moonlite focuser handles it fine and I've found the right amount of counter weighting to put at the bottom of the scope tube now.

One of those eyepieces that you can have in the focuser for a couple of hours as you move among galaxies and star clusters.

I think it's fair to say that the ES 17mm 92 has grown on me :thumbright:

Definitely the best Explore Scientific eyepiece that I've used to date and right up into Tele Vue build and performance territory.

Pity there are just two in this range - the 17mm and the 12mm. More focal lengths were promised by Scott Roberts, the President of Explore Scientific but have yet to surface. Maybe that will change soon ?

Anyway, this very large chunk of glass and alloy is earning it's keep tonight :icon_biggrin:

 

es1792dob12.JPG

Edited by John
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This eyepiece is on the top of my wishlist - which I've promised myself I won't rush to work my way through as I've only recently joined the astronomy world and surely I can't possibly know what I do or don't need yet, right?
Your write-up hasn't made it any easier for me to remain patient, hehe.  

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I've seen these at astronomy shows and they look good quality. They were on my shortlist due to the good eye relief when I was looking for a long-term eyepiece set up. If they were available in a wider range of focal lengths to be able to put together a consistent set of eyepieces I might have gone for these.

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I did have the 12mm as well for a while but the eye positioning with that one was even harder to get used to and I never really enjoyed using it. It went to a new home in Greece as I recall :icon_scratch:

The 17mm though I've persevered with and now it's paying off :smiley:

It fits well in between my 21mm Ethos and 13mm Ethos but cost a lot less than a 17mm Ethos !

 

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I liked the 17mm ES-92 so much that I bought the 12mm a year later.  A 23mm to 26mm version would be welcomed to give my 26mm Meade MWA the boot for good.

As far as eye positioning, try dealing with the 12mm and 17mm Nagler T4s.  Both are incredibly tiring to use due to their super finicky exit pupils.  The ES-92s are a dream to use by comparison.

Even with my eyeglasses off (exposing my raging astigmatism), I find I have to push in pretty far to see the entire field with the Ethos I've tried at star parties.  They seem more like the T2/T6 Naglers as far as eye relief in that you can't really hover back from them and take in the entire view.  I like that I can rest my glasses on the turned down eye cup of each ES-92 and easily take in the view without having to push in.  It makes for a more relaxing view.

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Sounds like a winner for the wallet and glasses wearers....good honest report John. 

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6 hours ago, Louis D said:

..As far as eye positioning, try dealing with the 12mm and 17mm Nagler T4s.  Both are incredibly tiring to use due to their super finicky exit pupils.  The ES-92s are a dream to use by comparison...

.

I have owned the 22mm T4 Nagler and found that comfortable and easy to use but I have heard that the 12mm and 17mm T4's are not quite as nice in that regard.

 

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4 hours ago, John said:

I have owned the 22mm T4 Nagler and found that comfortable and easy to use but I have heard that the 12mm and 17mm T4's are not quite as nice in that regard.

 

Correct.  Despite them all having the same AFOV and eye lens diameter, the 22mm version is fairly easy to take in the view while the 12mm and 17mm are more difficult.  I think it comes down to undiagnosed SAEP:

1732822435_SAEPFOVComparison1.thumb.jpg.73b6922ecbc6e059b940bf82ec2bd63c.jpg

I think this is also why the 12mm ES_92 is slightly more difficult to use than the 17mm version.  I find it interesting that SAEP grows within many eyepiece lines as the focal length shrinks (NT4, ES-92, AT AF70).  It seems to have something to do with the increasing power of the negative lens section of each eyepiece line.

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Nice looking glass and nicer looking price for such quality.

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