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Explore Scientific 25mm 100 degree eyepiece

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#26 TechPan6415

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Posted 02 October 2013 - 04:22 PM

Update, I continue to be really amazed by this eyepiece, especially with nebula filters under our super dark skies. Objects like the Veil, N. American and M42 are just spectacular in using it.

The ES 25mm 100 is now my second most used eyepiece, the 14mm version is the most used. Overall, a pretty amazing gain over my 30mm 82 degree.

#27 opticsguy

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Posted 08 October 2013 - 06:30 AM

Interesting reviews and comments about this eyepiece. My impression is most users here are using fast scopes f/5 and under. How is this eyepiece performing on long focus refractors? would be curious to try on my 8" f/13. I suspect a lot of the complaints might disappear???

#28 csrlice12

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Posted 08 October 2013 - 12:15 PM

+1 on the ES 14 100*, this is the one of the line where it all came together right...a fantastic widefield. The 20mm is good, I'm using it more and more, but I just don't see me ever giving up my mushroom top ES 82 24mm...now if the 9mm will ever get here...

#29 csa/montana

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Posted 11 October 2013 - 09:54 AM

Bashing ES and Scott Roberts - who I have met and who is not only a gentleman but a true innovator - is just off the mark. Hopefully, this competition will spur more innovation and even better prices all around.

Clears,

Agreed. I have seen and heard nothing but good from Mr Roberts. Like the eyepieces or not, I think we should be respectful.


+1

#30 Dr Morbius

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Posted 08 June 2016 - 11:16 PM

Interesting reviews and comments about this eyepiece. My impression is most users here are using fast scopes f/5 and under. How is this eyepiece performing on long focus refractors? would be curious to try on my 8" f/13. I suspect a lot of the complaints might disappear???

 So,  how does the ES 25mm 100 eyepiece work with higher focal lengths?


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#31 gdjsky01

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Posted 26 June 2017 - 11:50 PM

I don't post to CN very often, if at all. Most of you will not know me, and have no reason to trust me, or my judgement. So be it. And I am reviving an old thread. 

 

I have owned or still own an AP130EDT f/8, a TMB180 f/9, a TV101 f/5.4, a Litebox with a Swayze f/4.5 45cm mirror, a Teleport 14.5 with a Zambuto f/4.5, a Teleport Zambuto 7inch f/5.6, a Cave Optical 10 inch deluxe, a Starsplitter with a 25cm Zambuto f/4.5, a Starmaster 11 ELT, a Vixen 80mm f/12, and an Obsession UC 22. I have owned TV Naglers, TV Pantoptics, TV Plossls, Pentax SMC orthos, ES 100s in 20, 14, and 9mm FLs, UO HD orthos, Takahashi Orthos, and more.

 

I have observed through Lockwood 24 and 28 mirrors at f/3.7 and f/3.3. I have observed through a 48 inch f/4 scope using Zeiss orthos. 

 

NONE of that makes me an expert in optics. I know that. But whomever wrote the review of the ES 100 had a COMPLETELY different experience than I have just 3 nights ago.

I borrowed the ES 25mm from ES at a star party. I used it in an Obssession UC22 f/4.2 built last year. I used an original paracorr. No tuneable top.

 

That night, myself and my friends looked through the ES25, the 31mm Type 5 Nagler, and a Pentax 40mm XL. To a TEE, everyone thought the view through the 25 excellent. The 31mm was easier to see the field stop, but harder to position the eye (after all the exit pupil is enormous). The 40 gave very nice views, but seeing the field stop, even at 68* gave a soda straw type feeling. The 25mm OTOH had a smaller exit pupil, but to see the edges you had to move your head. And the very edges were not sharp. But the VERY edges. I am NOT an edge Astronomer. I am an observer. That is not to say they thought the 31 or 40 bad. No!!! Just 'different'.

 

Perhaps my friends, one or two being somewhat noted DSO observers, are not as 'discerning' as most of you are.  Or perhaps the 21mm Ethos is superior given the money. But my opinion this "Buy TV and cry only once" is not accurate and a 'put down' of the 25mm. Maybe things are improved since the original post. However I feel, since I bought one, compelled to say I think this review is inaccurate. 

Final fair warning. I have known the owner of ES as a 2 or 3 times a year casual acquaintance. However I have also been a friend of the local TV rep for 12+ years. 

Nothing above constitutes a review. And never believe 'The argument from authority'. I simply am stating an alternative viewpoint based on MY experience in the past 72 hours. (Not alternative facts.) 

Of course the best thing here is, "I borrowed ... " meaning try before you buy.


Edited by gdjsky01, 27 June 2017 - 12:01 AM.

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#32 Starman1

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Posted 27 June 2017 - 12:28 AM

The current price of the 25 Explore Scientific is nearly the same as the 21 Ethos, so price isn't the comparison to make.

You will cry if buying either one.

The 25mm, however, has the largest field of any 100° 2" eyepiece out there.

It's 13.3% wider of field than the 21 Ethos.

That means that at the field stop edge of the 21 Ethos, you're 93.4% of the way from center to edge.

So it's likely that whatever happens in that last 10% isn't going to matter much.

And the eyepiece makes a great combo with the new 17mm 92°.


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#33 turtle86

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Posted 27 June 2017 - 11:00 AM

I don't post to CN very often, if at all. Most of you will not know me, and have no reason to trust me, or my judgement. So be it. And I am reviving an old thread. 

 

I have owned or still own an AP130EDT f/8, a TMB180 f/9, a TV101 f/5.4, a Litebox with a Swayze f/4.5 45cm mirror, a Teleport 14.5 with a Zambuto f/4.5, a Teleport Zambuto 7inch f/5.6, a Cave Optical 10 inch deluxe, a Starsplitter with a 25cm Zambuto f/4.5, a Starmaster 11 ELT, a Vixen 80mm f/12, and an Obsession UC 22. I have owned TV Naglers, TV Pantoptics, TV Plossls, Pentax SMC orthos, ES 100s in 20, 14, and 9mm FLs, UO HD orthos, Takahashi Orthos, and more.

 

I have observed through Lockwood 24 and 28 mirrors at f/3.7 and f/3.3. I have observed through a 48 inch f/4 scope using Zeiss orthos. 

 

NONE of that makes me an expert in optics. I know that. But whomever wrote the review of the ES 100 had a COMPLETELY different experience than I have just 3 nights ago.

I borrowed the ES 25mm from ES at a star party. I used it in an Obssession UC22 f/4.2 built last year. I used an original paracorr. No tuneable top.

 

That night, myself and my friends looked through the ES25, the 31mm Type 5 Nagler, and a Pentax 40mm XL. To a TEE, everyone thought the view through the 25 excellent. The 31mm was easier to see the field stop, but harder to position the eye (after all the exit pupil is enormous). The 40 gave very nice views, but seeing the field stop, even at 68* gave a soda straw type feeling. The 25mm OTOH had a smaller exit pupil, but to see the edges you had to move your head. And the very edges were not sharp. But the VERY edges. I am NOT an edge Astronomer. I am an observer. That is not to say they thought the 31 or 40 bad. No!!! Just 'different'.

 

Perhaps my friends, one or two being somewhat noted DSO observers, are not as 'discerning' as most of you are.  Or perhaps the 21mm Ethos is superior given the money. But my opinion this "Buy TV and cry only once" is not accurate and a 'put down' of the 25mm. Maybe things are improved since the original post. However I feel, since I bought one, compelled to say I think this review is inaccurate. 

Final fair warning. I have known the owner of ES as a 2 or 3 times a year casual acquaintance. However I have also been a friend of the local TV rep for 12+ years. 

Nothing above constitutes a review. And never believe 'The argument from authority'. I simply am stating an alternative viewpoint based on MY experience in the past 72 hours. (Not alternative facts.) 

Of course the best thing here is, "I borrowed ... " meaning try before you buy.

Jeff,

 

Thanks for your post.  I had a similar experience trying out an ES 9mm 120 degree eyepiece that had been loaned to me. I had previously read quite a few negative comments about it being soft towards the edges. In my own use, what I found is that while it wasn't perfect at the very edge, it really wasn't all that bad at the very edge (at least with a Paracorr), and it was certainly plenty sharp on axis. On the whole it was excellent, and I remember having some wonderful views of M3, M5 and M13 with it.  Kudos to ES for making the ES 9mm 120, 17mm 92, and 25mm 100 eyepieces available.  Nice to have choices. I would certainly encourage anyone intrigued by these eyepieces to at least borrowing them and giving them a try.


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#34 Starman1

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Posted 13 August 2017 - 04:56 PM

Interesting reviews and comments about this eyepiece. My impression is most users here are using fast scopes f/5 and under. How is this eyepiece performing on long focus refractors? would be curious to try on my 8" f/13. I suspect a lot of the complaints might disappear???

The author did use a barlow to change the light cone to f/8, but note that while this may significantly reduce the f/ratio-induced aberrations, like astigmatism, it will not reduce aberrations like coma from his f/4 mirror.

It's my impression that the view is unlikely to be any better than my f/5 newtonian with a Paracorr II (which reduces coma to the f/13 area and flattens the field).  My focal length is then 1825mm with the same ROC.

An 8" f/13 has a 2642mm focal length, but the ROC is around 881mm, so field curvature is more likely in your setup, even if coma is eliminated.

As for vignetting, the secondary mirror of my newt drops the illumination by 30% at the edge.  The star diagonal and focuser drawtube may have a similar effect in the refractor, though I am not certain of the degree since

it will depend on where in the travel of the focuser the eyepiece comes to focus.

If you try one, it would be quite interesting to hear your comments.



#35 jrbarnett

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Posted 16 August 2017 - 09:47 PM

I'll add to Richard's excellent review with a few comments of my own, and some suggestions:

I spent a fair amount of time with the 25mm in my 12.5" under dark skies, too.

My comments could be similar to yours, since I use both a 31 Nagler and a 21 Ethos, in a 12.5" f/5 scope with Paracorr.II.

Here is what I found:

1)distortion--obviously corrected for AMD, because RD is noticeable. It's obviously corrected for nighttime, astronomical observation. This is not a negative, just a comment.

2)vignetting--obviously significant, since it's easily visible in both day AND night viewing, starting about 80% of the way to the edge. Not unexpected, since the field stop is a little larger than would be expected in a 2" barrel with this AFOV (probably why TeleVue stayed away from this focal length), but also minimally noticeable at night, and pretty much only if you let the moon drift toward the edge of the field.

3)light scatter--not great. When the crescent Moon is in the field, the light from the lighted part bleeds over to the earthlit part and reduces contrast. Averted vision shows this.
When the Moon is outside the field, it's obvious which direction the Moon lies.
More aggressive baffling would have reduced the FOV, I believe. Not a great lunar eyepiece, therefore, but since the eyepiece is highly unlikely to be used as a lunar or planetary eyepiece in any scope, this may be a non-issue.
Suggestion: use for all purposes except Moon viewing.

4)astigmatism correction--not the best. Even in the Paracorr, star image degradation starts a little more than half-way to the edge and gets suddenly worse at about the 90% point.
Going back and forth through focus on a star near the edge, the astigmatism at the edge is obvious.
It's better than many 80 degree eyepieces, though.
Suggestion: Use as a finder eyepiece for really low power.

5)lateral color. Star images become prismatic near the edge, and moving the eye only partially eliminates this. Holding the eye in the wrong place with an Ethos can do this too, but changing the position of the eye eliminates it. In this case, it can't be eliminated, AND the blue ring at the edge is very noticeable on the Moon; otherwise not at all.
Suggestion: Experimenting with eye placement is essential to reduce this effect.

6)internal reflections. With Sirius slightly outside the field of view, there is a semi-circular ghost in the field. The center of that circle is where Sirius is.
The ghost is not evident when Sirius is in the field, but it's obvious that reflection from the interior wall of the eyepiece barrel, or the side of a lens, or the filter threads at the bottom, or a modestly bright spacer ring visible near the bottom causes this. It could have been fixed with a baffle, probably, but wasn't, and for the reasons I mentioned above.
Suggestion: I would recommend darkening the filter threads on the bottom of the eyepiece and the bottom of the barrel itself.

7)image sharpness on axis and in the center 50% of the field is very good. If a user mainly looks here, it will be an engaging eyepiece to use.
Suggestion: Use for objects that can be framed well by the field of view.

8)field curvature. In the Paracorr, I didn't really notice anything that I couldn't eliminate by careful focusing (I'm 62). But without the Paracorr, though coma dominated the edge, (and astigmatism), I could focus the edge a little better and when I did, it defocused the center. Since my scope has a 1587mm focal length sans Paracorr (1825mm with), I would bet the field curvature of the eyepiece matches the scope and augments it to create a noticeable curvature. It really didn't matter, though, since FC wasn't the biggest issue at the edge, and it was fully eliminated in the Paracorr by focusing partway out from center.
Suggestion: Don't focus on a star in the center, but partway out and the entire field will be in better focus. Astigmatism and lateral chomaticism are reduced by having a better focus over the entire field.

9)coloration. Well, I'm pretty insensitive to this. Even if the tint were slightly yellow, my eye would see it as white 2 seconds after looking through the eyepiece. It's one of the reasons I regard any discussion of tint as a "tempest in a teapot". You might notice it if quickly changing eyepieces, like in a turret, but otherwise? It's only important to me if it reduces the ability to see colors in stars or objects. if I see a tint, it's STRONG. But in eyepieces? REALLY subtle. I saw none in this eyepiece, even on the Moon.

It would be interesting to see if a simple black ring on the bottom of the eyepiece might eliminate an internal reflection (as it has done on some other eyepieces) or whether simple blackening of the filter threads helps. Had internal baffling been more aggressive, and the FOV reduced to, say, 90 degrees, this eyepiece could easily have earned a better review.

[Excerpted from a March 17th post and somewhat enhanced]

I wish Televue would design a 25mm Ethos - to give ES a better design to start from.  :grin:

 

- Jim


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#36 faackanders2

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Posted 07 September 2017 - 08:45 PM

Such an interesting review that articulates what I don't have the experience to articulate myself! In short, I struggle with the 25mm - I thought for sure this would be an easy replacement for the ES30 82*, but here I am months later and I can't bring myself to sell the 30 (or the 25) but know that one of them "should" go for practical reasons.

Not that much I can add but to confirm this EP really is a nightmare on the moon (I do like to look at the moon wide-field occasionally) with a bright orange ring all the way around. I struggle somewhat with eye-placement as well, black-outs are common as I try to scan the sky - not excessive but it certainly detracts from the immersion experience. I do also find the light scatter to be excessive.

Finding a spot to focus well off-center does seem to create a nice balanced pleasing view, and it's nice to have the extra magnification in such a wide-field when compared to the pinpoint tighter view of the 30mm. Maybe one more night with this review in mind and I can finally come to a conclusion on whether to keep or let someone else try the 25mm...

The bright orange ring of fire also appears of the moon with 9mm 120AFOV ES, so for the moon I prefer 10mm 100 AFOV TV.



#37 faackanders2

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Posted 25 May 2018 - 08:24 PM

I wish Televue would design a 25mm Ethos - to give ES a better design to start from.  grin.gif
 
- Jim

This does not give ES the credit they deserve, unless you are just being sacastic.

#38 Dr Morbius

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Posted 03 June 2018 - 09:30 PM

So, has anyone tried this eyepiece (ES 25mm 100 deg) in a refractor of f/12 or f/15 or so? Must have by now I'm sure.



#39 Neptune

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Posted 10 June 2018 - 09:37 AM

I am wondering how this would perform in my C11 Edge. After reading all the reviews I am left wondering, but not ready to take the plunge.


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#40 Procyon

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Posted 16 June 2018 - 07:22 PM

I am wondering how this would perform in my C11 Edge. After reading all the reviews I am left wondering, but not ready to take the plunge.


Love it on CPC 1100. Primarily for the huge view and eye placement/comfort. A purist will find some faults but for me and my scope it's great.

Edited by Procyon, 16 June 2018 - 08:03 PM.

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#41 Neptune

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Posted 17 June 2018 - 09:31 PM

Love it on CPC 1100. Primarily for the huge view and eye placement/comfort. A purist will find some faults but for me and my scope it's great.

So some of the faults would be?  bloated stars, sea gulls,etc?  My Edge has no field curvature, so wondering how that eyepiece would work in this scope?

David



#42 Procyon

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Posted 17 June 2018 - 09:42 PM

So some of the faults would be? bloated stars, sea gulls,etc? My Edge has no field curvature, so wondering how that eyepiece would work in this scope?
David

A more experienced friend noticed astigmatism on the edges in my scope with the 25 ES 100. In an F/4.5 16" dob another friend noticed even more astigmatism. I compared it to a 26mm Nagler T5 and noticed more correction off axis in the 26mm Nagler. In the end I kept and definitely like the 25 ES 100 more for the huge view, great eye placement and comfort. I sold my 22 and 26mm Naglers after 2 nights out with it. Contrast and dark background also seemed better in the 25 ES 100, to me.

Edited by Procyon, 17 June 2018 - 09:46 PM.

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#43 Neptune

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Posted 09 July 2018 - 09:49 AM

Just picked up a 31mm Nagler. It has a smidge more field of view than the ES 25mm 100 and should be easier to view that field, ie less head & eyeball movement. Should be here in a few days, but we just entered into Monsoon Season, figures.


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#44 Procyon

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Posted 09 July 2018 - 10:37 AM

Just picked up a 31mm Nagler. It has a smidge more field of view than the ES 25mm 100 and should be easier to view that field, ie less head & eyeball movement. Should be here in a few days, but we just entered into Monsoon Season, figures.

Hi Neptune, I have the ES 25 100 and have tried the superb 31mm TV Nagler, I find the ES 25 100 easier to view through and more comfortable. It's actually the most comfortable eyepiece I have. No head or eyeball movement required to view the entire field for me. It's also making me want to sell the 32mm Masuyama 85. 


Edited by Procyon, 09 July 2018 - 10:37 AM.

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