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ES14 v.s. Ethos 13

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#1 Tamiji Homma

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Posted 30 April 2009 - 12:45 PM

Hi, all.

Daniel forwarded me URL to his writeups about ES14 and Ethos 13.

Here you go...
http://danielmounsey.com/?p=40

Enjoy.

Tammy
 

#2 t.r.

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Posted 30 April 2009 - 12:52 PM

Tammy, Do you have a link to the 5" refractor shoot-out as well?
 

#3 Tamiji Homma

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Posted 30 April 2009 - 01:03 PM

No, I don't.

I am not sure he finished writing it :)
I missed Tuesday star party so I didn't have a chance to ask.

Tammy
 

#4 Tom T

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Posted 30 April 2009 - 01:07 PM

Thanks Tammy, that was an interesting read.

A few things I happened to notice:

In one sentence Daniel apparently equates field flatness with pincushion, rather than a curved field. This is a rather curious misstatement. I think he may want to either rephrase or brush up on his understanding of rectilinear distortion a bit. I agree that rectilinear distortion is much easier to spot in the daytime because of the preponderance of straight line daytime targets - trees, cars, fences, etc, but I'm not aware of any method by which it would actually be reduced at night - however, it would be far, far less noticeable.

As an aside while checking his statement on pincushion in the ES14 I'll note that I felt there was a more pincushion in the ES than the Ethos (so much that it got me wondering just how similar or dissimilar the designs actually are), but I was looking through it during the day at NEAF and I didn't have an Ethos immediately at hand.

I also think he's misidentifying kidney beaning. He might want to take a closer look at the difference between spherical aberration of the exit pupil and blackouts caused by improper eye placement. Given the fact that he's not complained about kidney beaning during the day, I suspect he's actually vignetting the exit pupil by improper eye placement.

Another thing I read with interest was, as Daniel noted, this is still a production sample, not an actual shipped product. I've seen areas where the two ultimately differed in significant ways (both good and bad). It will be interesting to see if there are any differences in the first production batch.

Finally, I also think he should have tested them in fast flat field scopes - something like the NP127, NP101 or an FSQ - from a design standpoint those present, quite possibly the cleanest fields to the focal plane of any scope around and are the best way to separate scope aberrations from eyepiece aberrations. In determining field curvature for example, it could be critical. One eyepiece may have the same direction of curvature as the telescope and have an additive effect, and the other may curve against the telescope's field (subtractive) and actually serve to help correct it.

Overall, an entertaining read - thank you for posting it on the forums, and thanks to Daniel for writing it up. I'm looking forward to hearing more reports from other observers and actually seeing one myself at some point.

T
 

#5 t.r.

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Posted 30 April 2009 - 01:08 PM

Thanks, and keep us informed on that...Good read on the ES14!
 

#6 Tom T

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Posted 30 April 2009 - 01:12 PM

I was also wondering - did he say how many nights he compared them over? I think I missed that.

And BTW - is there an actual way to leave comments about the post over on his blog? I saw something that said "Leave a comment", but couldn't find an actual way to do it.

I'm feeling a bit old and slow today. :lol:
 

#7 Jim7728

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Posted 30 April 2009 - 01:14 PM

Great review!
Going on memory when I attended NEAF, I thought the ES14 was a little more sensitive to eye placement for daytime viewing than the 13mm Ethos. YMMV.

That said, if I did not already own a 13mm Ethos, I'd maybe buying the 14ES. ;)
 

#8 mandotrout

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Posted 30 April 2009 - 01:27 PM

Can you actually BUY an ES ep now, or are they still just "coming soon"?
 

#9 hfjacinto

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Posted 30 April 2009 - 01:29 PM

Great review. If I only had $400 and if I needed a 14 MM. Now if ES comes out with 8 to 10 MM EP and I can convice the CFO that this is a need, I am getting one.

BTW Anyone want to take bets on how long it will take this post to get locked?
 

#10 Tamiji Homma

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Posted 30 April 2009 - 01:29 PM

BTW - is there an actual way to leave comments about the post over on his blog? I saw something that said "Leave a comment", but couldn't find an actual way to do it.


Hi Tom,

I was able to leave comment. You might want to try again :)
You need to fill name and email address to post, I think.

Tammy
 

#11 hfjacinto

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Posted 30 April 2009 - 01:30 PM

Great review!
Going on memory when I attended NEAF, I thought the ES14 was a little more sensitive to eye placement for daytime viewing than the 13mm Ethos. YMMV.

That said, if I did not already own a 13mm Ethos, I'd maybe buying the 14ES. ;)


I think it was sensitive because they kept dunking it and not cleaning it correclty.
 

#12 Tom T

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Posted 30 April 2009 - 01:31 PM

Thanks Tammy, I'll look again.

:lol:

I'm blind, it's at the bottom of the article, big as day.

T
 

#13 Tom T

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Posted 30 April 2009 - 01:36 PM

Great review!
Going on memory when I attended NEAF, I thought the ES14 was a little more sensitive to eye placement for daytime viewing than the 13mm Ethos. YMMV.

That said, if I did not already own a 13mm Ethos, I'd maybe buying the 14ES. ;)


I think it was sensitive because they kept dunking it and not cleaning it correclty.


That might well explain a few other things, but I'm not sure how it would affect sensitivity to eye placement.
 

#14 feng

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Posted 30 April 2009 - 03:49 PM

“While viewing the Moon in either telescope, I did notice a small reflection caused by light reflecting off my own eyes on top of the 14mm ES that was not at all visible while using the 13mm Ethos.”

I can see the same reflection on my 3.5t6 while viewing the moon.
 

#15 zjc26138

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Posted 30 April 2009 - 04:28 PM

Great review Daniel, and thanks for posting it Tammy!
 

#16 Teal'c

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Posted 30 April 2009 - 04:42 PM

What the heck...for $399.00, I got on the list a while ago.
 

#17 Lawrence Sayre

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Posted 30 April 2009 - 05:03 PM

Daniel, that was a fantastic review! It's got me drooling for a 14mm ES. The only thing holding me back from purchasing one is my support for my three children (OK, young adults) in college at the same time.
 

#18 Daniel Mounsey

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Posted 30 April 2009 - 09:59 PM

Tom,

I agree with your statement. Field curvature usually causes the issues discussed rather than pincushion and I added some clarification regarding my statement "per your comments", so there were less misunderstandings. The problem is that when I moved the eyepiece left and right to check for either aberration, there was unquestionably a tad more pincushion in the 13 Ethos and so it's difficult to say for sure what it could be. I do agree with you though and was totally baffled and although what I said may not make sense, not everything may pan out the way the books say they should. I've seen other instances where the technical stats didn't add up either because of how certain eyepieces behave in different scopes. Yes, you can see rectilinear at night if you know what to look for but there's just nothing straight to relate it to while viewing stars. I'll explain my issue regarding kidney bean shortly.

Sorry so late Tom, Here are some comments from Mike Hosea's essay below.

"There's also a condition called "spherical aberration of the exit pupil", which isn't really spherical aberration at all. I guess it's just that the cross-sectional diagrams you might draw to show it are reminiscent of diagrams depicting longitudinal spherical aberration from a spherical mirror. When this problem is present it can be difficult to see the edge of field without losing some of the middle of the field in a kidney bean shaped blackout area. When you pull back a little the center is then clean, but the edges can't be seen because the eye isn't close enough to the eyepiece. I hasten to add that just because you have some problems with blackouts doesn't mean there is spherical aberration of the exit pupil. In most cases you simply need to take the care to center the eye over the exit pupil. This is especially true when there is an abundance of eye relief. Furthermore, even if there is some spherical aberration of the exit pupil, it isn't a sharpness issue, and it isn't any problem at all if you don't have any problem avoiding blackouts with your normal usage. Often it is only an obtrusive problem for daytime, terrestrial and lunar observation. The discussion above has pretty much assumed that the telescope per se is not contributing anything in the way of aberrations"
 

#19 Daniel Mounsey

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Posted 30 April 2009 - 10:06 PM

Daniel, that was a fantastic review! It's got me drooling for a 14mm ES. The only thing holding me back from purchasing one is my support for my three children (OK, young adults) in college at the same time.


Lawrence, thank you. I also got your PM and I will check the focus and get back to you. I really liked the question you raised about where the focus point is for each eyepiece and I completely forgot to add that to my review. I will be sure to check that. There's always something to learn about enhancing a review. :)
 

#20 Daniel Mounsey

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Posted 30 April 2009 - 10:18 PM

I was also wondering - did he say how many nights he compared them over? I think I missed that.

And BTW - is there an actual way to leave comments about the post over on his blog? I saw something that said "Leave a comment", but couldn't find an actual way to do it.

I'm feeling a bit old and slow today. :lol:


We did two sessions with two prototypes and another session with the production model. Yes, you can leave a comment at the bottom of each review.
 

#21 Jim Romanski

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Posted 01 May 2009 - 10:13 AM

With regard to field curvature, you don't mention what kind of scope the 80mm refractor is. I have come to be skeptical of field curvature claims unless I read that said eyepiece was tested in a flat field scope such as the NP101/NP127 or other scope with a field flatener.

I also wish you would spare us the discussion of your distaste for the barrel undercut. It's been done and over done here. All the Televue eyepieces have it so it's really not relevant to the comparison and I found the discussion distracting. I know many people don't like it but some of us in the minority think it's a great idea. In fact I would argue that it's more useful as an eyepiece safety feature than the additional 21% Nitrogen in the ES eyepiece. You just have to remember to loosen the thumbscrew more with compression rings to clear it.
 

#22 Tom T

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Posted 01 May 2009 - 12:35 PM

Tom,

I agree with your statement. Field curvature usually causes the issues discussed rather than pincushion and I added some clarification regarding my statement "per your comments", so there were less misunderstandings. The problem is that when I moved the eyepiece left and right to check for either aberration, there was unquestionably a tad more pincushion in the 13 Ethos and so it's difficult to say for sure what it could be. I do agree with you though and was totally baffled and although what I said may not make sense, not everything may pan out the way the books say they should.


In a private conversation this morning, a buddy and I were discussing the fact that - "Science does Work" - and modern life is kinda based on that. In other words, things DO work out like they are in the books, and observations can be explained if you know the basics of how the image is formed, and what's involved in a particular observation. If one's statements run contrary to the laws of optics, then it's most likely one's statements, testing and or understanding that must be revisited rather than the science. I know that's been true for me.

You make a statement about more rectilinear distortion in the ES, and more pincushion in the ethos. There's a problem with that statement. Pincushion is a subset of rectilinear distortion. Did you mean you found the ES to have more barrel distortion than the Ethos had pincushion? Did you really mean another type of distortion altogether - angular magnification distortion perhaps? Can you clarify your statements a bit? What do you mean by you moved the eyepiece left and right? In the scope? Changed viewing position?

Additionally, I also noted you made comments about coatings correcting for the warm hue - personally I think it's most likely more due to design and glass type. FWIW, I confirmed with Tele Vue that they use the same coating technology on all of their current eyepiece lines from Plossls to Ethos.

I've seen other instances where the technical stats didn't add up either because of how certain eyepieces behave in different scopes.


Not sure what you mean by technical stats, but yes - obviously eyepieces do work differently in different telescopes. For example if you have a scope that presents a curved field and an eyepiece that has a curved field, those fields can either be additive (resulting in a greater focus shift from center to edge) or subtractive (resulting in better uniformity of focus across the field). This is a reason - if you want to be splitting hairs about eyepiece performance (as opposed to eyepiece/telescope performance) testing in a flat field scope is so critically important.

Yes, you can see rectilinear at night if you know what to look for but there's just nothing straight to relate it to while viewing stars. I'll explain my issue regarding kidney bean shortly.


The easiest way to see rectilinear at night is to pan the telescope while looking through the eyepiece. If the stars follow straight lines across the field - edge to edge and seem to get closer together as they near the edge of the field- then rectilinear distortion is well corrected. If they travel in arcs moving outward, then there is pincushion. Be aware, there is some natural pincushion resulting from angular magnification correction that preserves the relative distance between stars at any point in the field, one option for the designer of astronomical eyepieces is to leave this in place so the majority of the field is well corrected. I've heard that some binocular eyepieces correct for rectilinear so that telephone poles look straight, however they get closer together at the edge of the field. This is the barrel distortion that seems to squeeze planet shapes near the edge of the field. Because I don't tend to observe at the extreme edge of field I’ll trade some of this residual pincushion for straight lines - and preservation of a cluster’s look as it crosses the field in an undriven scope - any day. But that's my preference. Some designs reflect that, others make other compromises. From what I've seen, design is an exercise in trade-offs.

It's easier to check for certain aberrations during the day as they stand out then - however, one should always remember that these are astronomical eyepieces and take night time usage as the primary indicator of their performance.

The term "Kidney Bean" used properly, describes spherical aberration of the exit pupil. The kidney bean blackout occurs when your eye’s pupil is too small and vignettes some of the rays that form the exit pupil. This causes a kidney bean shaped area to blackout and moves as your eye moves forward and back from the exit pupil. This is different from the typical blackout that amateurs complain of and frequently incorrectly label kidney bean. FWIW, from your description, it appears to me that you're vignetting the edges of the exit pupil by not having your eye in the proper position. If you are too close to the eyepiece and “inside” the exit pupil this will also cause blackouts, but they aren't the same thing as true kidney beaning. Typical, true, kidney bean in an eyepiece is most obvious in the daytime because of the smaller size of your pupils, and the fact you're seeing the blackout against a bright (as opposed to dark) background. The reason I don't think you're seeing actual kidney beaning is because you didn’t mention it in your daytime observing report - only on deep sky observing (when your pupil is largest).

FWIW, there is a lot of good information about various aberrations including distortion in Telescope Optics by Rutten & Van Venrooij.

T
 

#23 j3ffr0

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Posted 01 May 2009 - 12:42 PM

I think the barrel undercut is worth mentioning. I'm glad there is a manufacturer who is willing to listen to give the majority of observers on this one. All things being equal, me and my focuser would certainly prefer smooth side EPs.
 

#24 Jim Romanski

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Posted 01 May 2009 - 03:30 PM

I think the barrel undercut is worth mentioning. I'm glad there is a manufacturer who is willing to listen to give the majority of observers on this one. All things being equal, me and my focuser would certainly prefer smooth side EPs.

I'm fine with it being mentioned and that many prefer it. I just think that given all the posts on CN complaining about it that it's really a seperate issue. I thought that the write-up spent more time on this than I wanted to hear. I can see that one is undercut and the other isn't and I know what that means. I want to hear more about what I don't know, namely how are the views through them.

BTW, I remember vividly many years ago seeing a 13mm Nagler T1 slide out of a focuser and bounce on the ground. The guy thought he had the thumbscrew tight enough but it slid out. :nonono:

It wouldn't have happened with an undercut.
 

#25 Daniel Mounsey

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Posted 01 May 2009 - 06:12 PM

Post deleted by jrcrilly
 






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