Telescope Reviews: ES14 v.s. Ethos 13

Daniel,

We're still not communicating.

Your initial statement was not a contradiction, it simply does not make sense.

There are two types of distortion that we need to worry about for astronomical eyepieces. Angular Magnification Distortion and Rectilinear Distortion. Further rectilinear distortion can be classed as one of two types - Pincushion or Barrel.

Pincushion and Barrel are a subsets of RD, RD is the superset.

To use an analogy, in saying that the Ethos has more pincushion and the ES has more RD - well, it's like you're talking about two cars, and you say one car is a sedan, but the other car is more of a car. They are both cars, but sedan is the particular type.

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that the 14ES appeared a tad less straight than the Ethos, but once again and as I stated in my review, it was very subtle.

I think this statement, however, is indeed a contradiction with what you previously wrote.

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Regardless and Ironically, the center of the field still seemed more pinched along its "center" more so in the 13 Ethos during the night while viewing the stars, while the 14mm ES appeared more uniform, flatter or corrected along most of the field of view and everyone agreed, myself included.

Ok. But here again, we run into problems - what do you mean by flatter? It too has an optical definition. Do you mean in terms of Distortion (either AMD or RD) or Field Curvature? These are fundamentally different aberrations. Optically to describe it as a flat field specifically refers to a lack of field curvature. (IE - focus does not change across the field.) But your statement sounds like you're talking about distortion.

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In your defense, perhaps that part of the review is a bit vague and should be more clearly stated, but remember that these eyepieces have huge fields of view and a lot can happen in that field. You can't just lay optical laws in stone and say that's exactly how it's going to appear at night.

In the case of distortion, yeah - I think you pretty much can. There are lots of other things that can be affected by implementation (scatter for instance), but distortion is a design characteristic.

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That wouldn't be open minded now would it?

It's not a case of being open minded. It's a case of understanding what's going on and why. These are basic optical concepts with established definitions.

You rather dismissively state that book learning without experience is of limited value - and there's certainly truth to that - as far as it goes. But ideally, people develop BOTH their education and their experience. Understanding without seeing is one thing. Seeing without understanding is another. IMO, everyone, but especially people who attempt to educate others (especially where technical items are concerned) should have or consider it a must to develop a good balance of both.

It's an ongoing process. In education we use the phrase "Lifelong Learner".

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I gave the slight edge in light through-put and contrast to the Ethos.

In my opinion, it isn't wise to sell certainty with optical terms and definitions without "experience". It's better to remain open minded about what you appear to be seeing and try to express it constructively. Quite frankly, it's very disappointing listening to some of the comments in forums with those who spend most of their time just reading and chatting yet, don't even have an inkling of experience in the field to back their claims. They read books and all the sudden they're optical experts. I'll give you an example. These discussions about OK4 vs. FPL53. If a person thinks it's a major concern, it's clearly an indication that they don't have the experience to realize they're asking the wrong question about their concerns.

The observers mind is polluted with confusion because things on paper are very misleadng and things DO NOT always behave as the papers claim and you of all people should know that Tom.

Daniel, there are at least two phases - design and implementation. Design absolutely goes by the book. It has to. People can't begin to design things if they didn't have some assurance they'd have a working product. To see what they may have overlooked, as well as what may be implementation issues (that may not have been considered) you go through the prototyping and production prototyping process. When you're looking at a piece of gear critically it's important to know what is design and what is implementation. For example, IIRC Tak states the TSA has a design strehl of .992. We both know that does not mean every TSA has a strehl of .992, rather just that's the maximum design value - real world values will be lower. This is where a sound knowledge of theory comes it. It allows you to interpret what you see and effectively communicate it to others.

FWIW, I look at the times I'm confused (and there have been lots over the years) as an opportunity to merge practice and theory. I know the chances I'd develop a new optical theory are vanishingly small, ergo when I see something in practice that apparently goes against the knowledge of theory I have, it's almost certainly because my knowledge is flawed. These are learning experiences, but you have to recognize them as such.

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This is why I tell many of my customers to STOP gargling the forums and get out in the field and get experience. That's why I hold my own star parties twice a month. I help beginners by allowing them to see through different telescopes in the field.

There's nothing wrong with people trying to read books and reviews but at least "apply it in the field" for crying out loud, there's a BIG difference. You and I have been members of CN since 2002, longer than everyone. I have over 3000 posts to my name. The purpose of the forums should be to offer constructive insight and meaningful forums.

I completely agree that people need to see what they like for themselves, and I always emphasize that, but that's not the point here.

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I'm shocked that Televue openly admitted the change in coatings. With regard to Televue saying they use the same newer coatings with all their eyepieces, your statement is very misleading and you're trying to discredit the comments in my review. First off, most of the Televue's in circulation DO NOT have the newer coatings and the reason I know that, is because Televue told me they were just starting to use the newer coatings during last years open house at OPT. If that's not the case, then you and I are getting conflicting stories from Televue. From what I was told, the green and red stickers on the plastic sleeves the eyepieces come wrapped in are simply to inform Televue which eyepieces have the newer vs. older coatings. I also know Televue is reading and following this forum very carefully.

Secondly, Televue has been around for over 30 years. I find it very unlikely that the majority of consumers who own Televue's all decided to gather up and throw their Televue's in the garbage and buy new ones within one year. What I sated in my review about the coatings was valid. The Ethos do have the latest, greatest coatings and most observers who compare them will see a difference.

Daniel, that's not what my earlier coating statement was about. The purpose of coating an optical surface in an eyepiece is (typically) to increase throughput. According to them, Tele Vue's coatings do not now, nor ever have, changed the tone from warm to cool. Yes, coatings have changed over the years. (In fact, Tele Vue told me they had changed coatings several years back, and just reconfirmed it for me.) And their coatings probably will continue to change as better ones come out. (I'd expect that from any manufacturer.) And yes, older eyepieces will have different coating - But again - that's not the point. The point was you specifically stated that their coatings were responsible for changing the hue from warm to a cooler tone. According to them that's incorrect. Period.

Look, we're going in circles here, so this is my last word on the subject.

As I mentioned above, I think it's very important to both see and understand if you're trying to educate others. If one does not, the educator may unintentionally do a disservice to both the learner and the field. Misconceptions, once formed, can be very difficult to overcome.

Learning is an ongoing process. You have a great love of astronomy, and for that I commend you.

Please consider the following: One does not have to present things technically, and many folks benefit from that immensely, but if someone is going to speak technically and in an authoritative voice about technical items, then they have a responsibility to understand and use the correct terms for what they are describing, as well an obligation to ensure that the information provided is as accurate as possible.

Thank you.

T

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