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Equipment Discussions >> Eyepieces

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thetortoise
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Reged: 07/25/12

Loc: Longmont, CO
ES25 100 - Shootout with ES30 82 and ES20 100
      #5739266 - 03/17/13 05:59 PM

Finally a clear night to really test out the ES25 100 (EP number 20 of the ES25 100 line)! I tested it from 11:00PM to 4:00AM on about forty Messier objects (trying to complete my leisurely multi-night messier marathon - down to about 15 remaining early morning objects).

First impressions: I have heard people say these EP's are "like" looking through a porthole into space (and I agree) - but the ES25 100 is the first EP that actually "looks" like a porthole - so much glass certainly bigger than the eye looking into it. I ordered 2 pounds of magnetic weights in anticipation of the EP being too heavy. With the weights I was pleased with the balance on my XT10G - balanced at 0 altitude through 85 degrees altitude. Also pleased that the crayford racks without problem and no slipping while viewing even with the coma corrector in place and my eye resting on the EP. Very pleased with the weight and mechanical performance as I was prepared for worse with my little scope (see picture below).

Viewing: First of all, I love the views through my ES20 100* and my ES30 82*. Wide-field is my favorite thing and thus the ES25 100 had a siren's call for me. With the ES30 having the same field-of-view (FOV) as the ES25 100 I was most interested in seeing if I could replace the ES30 to recoup some cost. All night I am switching out the 25 with the 20 and 30 to compare the views on each object. First light with the 25 as the Leo triplet - sans the NGC 3628 portion (or so I thought). At this point my eyes are not completely dark adapted but M65 and M66 look great. I drop in the 30 and instantly all three members are there, smaller, but clear as day. I change it out with the 25 and "of-course" there is NGC 3628, slightly washed out but obvious. Drop in the 20 and the character is similar to the 25. This pattern repeats throughout the night.

I should say (and it almost goes without saying) that my humble interpretation of correction to edge is just as good with the 25 as with the 30 or 20. This is a quality excellent EP.

Eye-placement seems more crucial with the 25 than with any of the other 82 or 100 degree EP's, As I move my eye around I am getting blackouts, something I have not experienced with my other ES EPs. Not terrible but I was a little frustrated with them as it detracted from the experience. This may improve with practice and as I become more familiar with this EP. I was thinking the test is almost unfair as I have used the ES30 extensively and know how to use it to maximize performance. Also, I was thinking that perhaps because the ES30 is sunken in while the ES25 glass is not, it makes eye placement more difficult? For example I just plop my eye right on the ES30 and there is some space between the glass as my eye, on the ES25 I suppose you can get too close.

With the lower exit pupil: 5.29 versus 6.35 with my ES 30, I expected to see more with the ES25 100, but that did not appear to be the case and I am unsure why. Am I more used to hunting faint objects with the ES30? I will say throughout the evening my impression of the ES25 improved as perhaps my brain adjusted to the different view and I got better at interpreting objects through it (it may not be fair to chase faint galaxies as a large proportion of my objects were last night and use that as the test but that is where I was on my messier marathon and what I could best see from my location).

To get away from the galaxy centric review: M13 was incredible through all three EP's though I would say the extra magnification here gave the ES25 the edge over the ES30 (but even better through the 20, 14, 9 etc). I am viewing here at about 3:00AM and am having the best views through this scope that I have ever had. I viewed this object extensively last summer so was curious to test it on this object after putting in my 1/20th secondary, flocking the scope, collimating with my new Cat's eye full set of tools, discovering I have an excellent primary that cannot be further corrected - etc. Picture perfect views through the full range of ES EP's I own here with a well cooled mirror and dark night with some, but not a great deal of turbulence (viewing Saturn with my 4.7 at 255x was pleasing though you could see the distortion) - I would call the viewing unusually good compared to what I have been seeing this winter.

As you may have surmised - my initial impression of the ES25 100 is mixed. It's mixed not because it's not a phenomenal EP, but because in character and field it is so close to the ES20100, while to my eyes the ES30 82 with the same FOV delivers a less magnified, though (and I admit subjectively and perhaps even unfairly) a more pleasing and user friendly view with no blackouts and easier galaxy busting.

I say perhaps unfairly because in reviewing my observing list, I have no open clusters, and this is where I expect the ES25 100 to really shine, From my observing location the double cluster and the Pleiades were out of my view for example and I would like to compare on those as I have spent many hours at the EP on those objects. I was looking forward to testing on the Wild Duck Cluster but it started to cloud over at 4AM and I had to call it a night before it came into view.

At this point the character between the ES30 82 and ES25 100 is sufficiently different that I am unsure I would want to sell off the ES30. But then, why would I keep two EP's with the same FOV? If it came down to it I believe the ES30 and ES20 would make a better pair than either EP with the ES25 and a much better value. I would also say I would rather have both the ES20 and ES30 than just the ES25 as a bridge between the two. I guess I am saying the ES25 does not seem essential, and on first-light, I was not blown away by the views and sometimes even frustrated when compared to the existing EP's. If tonight is clear I will test further from a point where I can test the star clusters to give a more balanced view. Please do let me know if you have any observing tips or suggestions for making this test more balanced (I'm sure some of the experts are slapping their foreheads on some of what I'm writing here - but I am not an expert by any means though I have spent "hundred(s?)" of hours at the EP and view any night there isn't heavy cloud cover.) Thank you.



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herrointment
Post Laureate
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Reged: 03/12/11

Loc: North of Hwy. 64
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: thetortoise]
      #5739322 - 03/17/13 06:21 PM

And all I could think to say was that I liked it!

Thanks for the thoughts!

JE


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: thetortoise]
      #5739390 - 03/17/13 06:50 PM

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.

Here is what I found:

1)distortion--obviously corrected for AMD, because RD is noticeable. It's obviously corrected for nighttime, astronomical observation.

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, 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.

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.

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.
This is not obtrusive.

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. 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.

8)field curvature. In the Paracorr, I didn't really notice anything that I couldn't eliminate by careful focusing. 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, 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.

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.

Overall rating: B+. It missed getting an A because of scattered light. The slight astigmatism and FC are minor and tolerable and may not be noticed 95% of the time. 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 help. Had internal baffling been more aggressive, and the FOV reduced to, say, 90 degrees, this eyepiece could easily have earned an A. But, even as is, it is a remarkable eyepiece, with a field only a trace smaller than the 31 Nagler, yet a magnification 24% higher.

For all we observers getting a little older (where our maximum pupil size is shrinking) and/or for those using a shorter f/ratio scope than used to be common (say, f/4-f/4.5), this eyepiece may be the perfect low-power "finder" eyepiece to replace those 30-32mm large field stop eyepieces.

On my own scope, the 4.35mm exit pupil is much easier to use than the 5.4mm of the 31 Nagler. I was actually contemplating a 26 Nagler as a low power, but now I don't have to sacrifice the big FOV to get a better focal length. I could see jumping straight from this to a 13-14mm 100 degree EP.
For the young guys out there, this might produce a dimmer image than a 30-31mm 82 degree. But for those of us with smaller maximum pupils, this could be a really nice low power viewer.

Hmmm.


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thetortoise
super member
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Reged: 07/25/12

Loc: Longmont, CO
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: herrointment]
      #5739391 - 03/17/13 06:50 PM

Thank you herrointment! I should also mention that the best part was getting to complete the ES100 set by purchasing from a fellow CNr!

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sopticals
professor emeritus


Reged: 03/28/10

Loc: New Zealand
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: thetortoise]
      #5739540 - 03/17/13 08:04 PM

Thank you thetortoise. Very good review. I have the ES82 30 and 24 as well as a TV Nagler 20mm T2, and find ES82s and Naglers performance pretty much "on a par". Was wondering about the ES100s. Again thanks for taking the time to post your impressions.

Stephen.(44deg.S.)


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thetortoise
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Reged: 07/25/12

Loc: Longmont, CO
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: thetortoise]
      #5739579 - 03/17/13 08:27 PM

Thank you Don! I have learned more about this pursuit from your knowledge and insights on here than I can even express.

I too noticed the slight astigmatism but assumed my mirror wasn't fully cooled as I didn't notice it throughout the night though it's likely my initial view of extra critical and my eye let it go after that as this is something that has never bothered me with any of the other ES 100's. Certainly not bothersome astigmatism.

On light scatter - this is something I notice with most if not all of the ES EP's so it didn't stand out for me. Since I was viewing such dim objects anyway I didn't notice it. It's most noticeable on Jupiter and the Moon with the rest of the line as well - to the point where I use the light scatter to zero in on the Moon and Jupiter rather than switching to the laser or finder. Certainly problematic if you are not using as a "feature". The brightest object I viewed was probably Saturn and the light scatter was either not noticeable or I wasn't paying attention to it as I can't recall it as I easily do for items like Jupiter (I did not observe Jupiter last night - perhaps tonight).

The rest of your list I am unable to comment on as I am not to that level of observing skill yet.

On the exit pupil - maybe my 34 year old eyes still easily manage the 6+ exit pupil of the ES30 82 though this will eventually change - this would certainly color my interpretation of the EP's.

Thank you for your insights!


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thetortoise
super member
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Reged: 07/25/12

Loc: Longmont, CO
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: thetortoise]
      #5739593 - 03/17/13 08:32 PM

Thank you Sopticals! I will say the performance of the ES24 82 is very similar to the ES20 100. I sold my ES24 82 though it is an exceptional EP for sure. I just liked the ES20 100 slightly better with the higher magnification with the same FOV. It was this experience that made me nearly certain I was would the same experience with the ES25 100 versus the ES30 82. For whatever reason this comparison was not as clear cut on first impression.

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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: thetortoise]
      #5739991 - 03/18/13 02:12 AM

Quote:


I too noticed the slight astigmatism but assumed my mirror wasn't fully cooled as I didn't notice it throughout the night though it's likely my initial view of extra critical and my eye let it go after that as this is something that has never bothered me with any of the other ES 100's. Certainly not bothersome astigmatism.



Yes, not severe.
Quote:


On light scatter - this is something I notice with most if not all of the ES EP's so it didn't stand out for me. Since I was viewing such dim objects anyway I didn't notice it. It's most noticeable on Jupiter and the Moon with the rest of the line as well - to the point where I use the light scatter to zero in on the Moon and Jupiter rather than switching to the laser or finder. Certainly problematic if you are not using as a "feature". The brightest object I viewed was probably Saturn and the light scatter was either not noticeable or I wasn't paying attention to it as I can't recall it as I easily do for items like Jupiter (I did not observe Jupiter last night - perhaps tonight).




OK, and not likely to be a problem in 99% of the circumstances in which this eyepiece is likely to be used, either. The only issue is when a magnitude 0 or brighter object is immediately outside the FOV. And, as you said, it IS a finding feature.
Quote:


On the exit pupil - maybe my 34 year old eyes still easily manage the 6+ exit pupil of the ES30 82 though this will eventually change - this would certainly color my interpretation of the EP's.




Not greatly, though. I have noticed that when the exit pupil of the eyepiece is the same size as my pupil or a little larger that my own eye has a little more visible astigmatism (the astigmatic star image, unfortunately, rotates with my head), but that when I use a little smaller exit pupil eyepiece the image sharpens right up. For me, that "Rubicon" is crossed at about 4.8mm of exit pupil. [When you have a lot of eyepieces to test, you can pin it down like that.] And, it may shrink as I get older.
I no longer feel confident to rate the edge quality of 30-32mm eyepieces, unless they're really bad, but 26 and down...OK.


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dcoyle
professor emeritus


Reged: 10/11/05

Loc: Turbulent but dark skies, N.M.
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: Starman1]
      #5740422 - 03/18/13 10:36 AM

Thank you, Tortise, for taking the time to write up your experiences.

Thank you, Don, for your additional insights.

Dan


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alackofcolor
member


Reged: 03/04/13

Loc: Cincinnati, Ohio
Re: ES25 100 - Shootout with ES30 82 and ES20 100 new [Re: dcoyle]
      #5740735 - 03/18/13 01:36 PM

This was exactly what I was looking for not too long ago! I ended up buying the 20mm eyepiece in the line instead of the 25mm.

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