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22 Nagler T4 especially prone to coating damage?

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#26 stevetaylor199

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Posted 12 December 2012 - 12:13 AM

I should have titled the thread with the wording 'prone to coating damage?' because that is what I really meant. I have changed it accordingly.


I was thinking that a coating "defect" like the one cited in a post above -- which was caught by TV, and prompted them to identify such a new eyepiece as a blem item -- is not the same as coating "damage" or "failure."

I think an interesting discussion could be had about how coatings can become damaged -- or appear to be damaged. Also, I am not familiar with coating delamination or flaking, and how such an exceedingly thin chemical layer could separate from the substrate in that manner and with that visual appearance.

#27 slack

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Posted 12 December 2012 - 12:42 AM

Also, I am not familiar with coating delamination or flaking, and how such an exceedingly thin chemical layer could separate from the substrate in that manner and with that visual appearance.


It may be thin, but I have felt the edge of flaked-off coatings on an eye lens with my fingernail.

#28 Starman81

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Posted 12 December 2012 - 01:04 AM

22mm Nagler T4 eyelens. None of what you see here was able to be cleaned off with Zeiss wipes nor 50/50 isopropyl alcohol + distilled water with a drop of dish soap.

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#29 Starman81

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Posted 12 December 2012 - 01:05 AM

12mm Nagler T4 eyelens in excellent condition, for comparison.

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#30 Eddgie

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Posted 12 December 2012 - 09:29 AM

This is exactly how the Radian that I sent back to Televue looked. I tried to clean it with alcohol. I tried glass cleaners and I tried everything else.

Under magnification, it even looked like damage.

As I said in my earlier post, Televue cleaned it with Acetone and the spots came off. They said it took some amount of effort, but that this was common for tree sap.

This does not look like coating failure at all to me.

From what I understand, when coatings fail, it is usually because the glass substrate was contaminated.

The coating does not form a molecular level bond with the glass, and when it comes off, it comes off in flakes with very irregular edges.

The top picture here does not look at all like a coating failure or even damage.

The picture here looks exactly like the tree sap that I mistook for damage (not failure) and that Televue was able to remove.

I see no evidence of coating failure in this picture. Looks like tree sap or some other foreign matter adhered to the coatings.

These are almost sure to come off with proper cleaning.

Dude.. It's a picture of a dirty eyepeice.

#31 star drop

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Posted 12 December 2012 - 09:42 AM

I have never had a problem with coating failure on any Televue eyepiece and some of mine are thirty years old.

#32 Starman1

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Posted 12 December 2012 - 11:50 AM

Data point of 1: I had a 22 T4 for well over a decade (almost 2) and it was cleaned numerable times. The lens surfaces looked like new when I sold the eyepiece (it was replaced with a 21 Ethos).

Data point of hundreds: I worked for several years for a large retailer of astronomy gear. Tiny pinholes in coatings, mostly visible only with a loupe, were very very common. In fact, the brand with the most commonly-seen coating pinholes was Pentax.
Of course, none of those pinholes ever affected the views through the eyepieces, and most were only visible at high power through a loupe.

Only the Very cheapest (largely plastic-barrel) eyepieces had coatings that rubbed off or were easily damaged.

I have seen, in the field, and over nearly 5 decades, tons of eyepieces with scratches in the coatings. These were caused, by and large, by improper cleaning techniques. Also, they have been mostly MgFl2-coated lenses, not multi-coated lenses.

I have also seen hundreds of eyepieces with what appeared to be tiny pinholes in the coatings (like that pic of the 22 above), and they all came off when cleaned. But I have seen some grime that neither alcohol nor acetone removed. When you have to resort to MEK or something equally as strong to clean a lens, you wonder what the heck the stuff was that got on the lens. [as an aside: I had some mascara streaks on an eyepiece after a star party that required 5 cleanings with MEK to remove. It was like cleaning rubber cement off the lens--it dissolved in the cleaning fluid and deposited itself over the entire surface of the lens. Points out how valuable long eye relief eyepieces are at star parties!]

#33 Paul G

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Posted 12 December 2012 - 12:49 PM

Looks like an eyepiece that needs cleaning. I have about 40 TV eyepieces, clean them after every use and the coatings are pristine after years of use and cleaning. I have found that some surface contaminants, particularly organics, look like coating problems but are not. Some of these won't clean off with Zeiss cleaning fluid, Kodak cleaning fluid, acetone, methanol, or MEK. They will, however, come off with saliva on the pad of one's thumb (tree sap in particular).

I've seen coating defects in a Meade SCT corrector, but it had a crazed effect and the coating flaked off in irregular shaped pieces. This pic just looks like a dirty eyepiece.

#34 stevetaylor199

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Posted 12 December 2012 - 01:44 PM

I have seen, in the field, and over nearly 5 decades, tons of eyepieces with scratches in the coatings. These were caused, by and large, by improper cleaning techniques.


I believe I am guilty of having inflicting these on a camera lens or two, which is why I am reluctant to clean anything, ever. Your point on those coatings being simple MgF2 is noted, though.

What is MEK?

Edit: thanks for answer below: methyl ethyl ketone. I'll look it up; I've always enjoyed chemistry.

#35 star drop

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Posted 12 December 2012 - 02:16 PM

MEK is methyl ethyl ketone.

#36 GeneT

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Posted 12 December 2012 - 02:18 PM

There are a lot of people who 'hate' TeleVue--and for no reason. I am suspicious of anyone who posts information of this type without any proof. :flame:



You know...

Is that really necessary? Did you miss the part about my appreciation and use of Tele Vue eyepieces? Or see in my sig that I use two Tele Vue refractors? A Tele Vue binoviewer? Or that I have come across defects with Pentax and other makes of eyepieces? Or the part about my experience with professional cine/TV coated optics?

C'mon, be objective. The odds that coating problems haven't occurred with all of the multi-coated glass that TV has produced would be astronomical. ;)


My main point is when we make allegations of this sort, we should provide the proof. Eddgie notes that in his opinion, the picture shown does not show coating defects, and Don also believes what the picture shows is a dirty eyepiece. Since the OP has photos of the eyepiece in question on another computer, I recommend he find and post the photo. Then we can see and evaluate for ourselves.

#37 GeneT

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Posted 12 December 2012 - 02:26 PM

C'mon, be objective. The odds that coating problems haven't occurred with all of the multi-coated glass that TV has produced would be astronomical.


You have raised a different issue. I agree that there well could be issues raised by the OP, but even if he is correct, we are generalizing from one data point, and that one data point exists in photos on another computer. I would have preferred a posting that identified the problem, what TeleVue offered in the way of a solution, whether or not TeleVue solved the problem, and a photo showing the problem. What we have at stake here is the professional reputation of an outstanding company. We need to be a little more precise when making comments of this sort, and avoid sweeping generalizations.

#38 Starman1

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Posted 12 December 2012 - 02:31 PM

By the way, the pinhole gaps in coatings to which I referred in an earlier post were much smaller than the ones in the picture of the 22T4. They were invisible to the naked eye and required magnification to see. They were, I believe, due to incomplete cleaning of the lenses before coating on a very small scale.
And they were invisible in use.

#39 slack

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Posted 12 December 2012 - 02:44 PM

There are a lot of people who 'hate' TeleVue--and for no reason. I am suspicious of anyone who posts information of this type without any proof. :flame:



You know...

Is that really necessary? Did you miss the part about my appreciation and use of Tele Vue eyepieces? Or see in my sig that I use two Tele Vue refractors? A Tele Vue binoviewer? Or that I have come across defects with Pentax and other makes of eyepieces? Or the part about my experience with professional cine/TV coated optics?

C'mon, be objective. The odds that coating problems haven't occurred with all of the multi-coated glass that TV has produced would be astronomical. ;)


My main point is when we make allegations of this sort, we should provide the proof. Eddgie notes that in his opinion, the picture shown does not show coating defects, and Don also believes what the picture shows is a dirty eyepiece. Since the OP has photos of the eyepiece in question on another computer, I recommend he find and post the photo. Then we can see and evaluate for ourselves.


In response to another's post, I shared a factual observation, based on professional experience, that I have seen failed (read: defective) coatings on TV eyepieces. It has come up before, and I have shared the same info before, and nobody has challenged the validity of my report. In fact, as I indicated (and provided a link to just one of many substantiating reports going back about a decade here), TV has acknowledged that it has occurred. I have spoken directly to TV about it.

The flaked off coatings that I have seen appeared nothing like what is pictured above. Based on the pics posted above, I would not wager on what caused them. You can, but I'll pass. However, when and if I can locate the pics I have of a defective 31mm T5, it should be obvious to any well informed person that it represents a failure of the coatings. I suspect that some people won't be convinced no matter what and, well, ignorance is bliss. With regard to my "data," I would gladly make a significant wager. ;)

As with most things like this, the truth is usually somewhere in the middle. Have there been coatings failures and defects with TV eyepieces? Of course. (It's interesting that a couple of TV dealers have posted suggesting otherwise, given that TV has acknowledged that their products do not magically levitate above any potential real world problem or defy statistical odds.) But are many reports of damage or other issues misattributed to a production defect? Of course.

#40 slack

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Posted 12 December 2012 - 02:54 PM

I would have preferred a posting that identified the problem, what TeleVue offered in the way of a solution, whether or not TeleVue solved the problem, and a photo showing the problem. What we have at stake here is the professional reputation of an outstanding company. We need to be a little more precise when making comments of this sort, and avoid sweeping generalizations.


I don't believe I've made any sweeping generalizations or spoken negatively of TV. To the contrary, I have explicitly defended TV in my postings on this issue.

With regard to my telephone discussion with TV about the failed coatings on the 31mm T5, as I reported, based on my explicit description they agreed with my diagnosis and stated there was nothing they could do to repair the eye lens. (Which we all know. They also can not repair the coatings on their scope objectives.) The out of warranty cost to repair the EP was not sensible. I sold it to someone with full disclosure.

This has little to do with the reputation of an outstanding company, other than my having bolstered that reputation by reporting on their common sense discussion with me about it (that bad *BLEEP* sometimes happens, even with their stuff), which stands in stark and positive contrast to a couple of dealers chiming in to denounce any negative reports from the real world, no matter how few and far between they might be.

#41 GeneT

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Posted 12 December 2012 - 08:23 PM

If I can locate the pics in the future (they are on a different computer), I will post pics of eye lens coating failure on a Nagler 31mm T5.


Show us the pics so we all know exactly what you are talking about.

#42 slack

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Posted 13 December 2012 - 12:20 AM

This is the only pic of the Nagler 31mm T5 with bad coatings that I can find at this time. The portion in the reflection of the lights, that appears bright white, had recently flaked off when that pic was taken (hence the sharper edges of that patch).

Posted Image

#43 GeneT

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Posted 13 December 2012 - 10:13 PM

This is the only pic of the Nagler 31mm T5 with bad coatings that I can find at this time. The portion in the reflection of the lights, that appears bright white, had recently flaked off when that pic was taken (hence the sharper edges of that patch).

Posted Image


Thanks for posting the picture. I am sure that there are some who are qualified will evaluate and comment on the condition of lens.

#44 slack

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Posted 13 December 2012 - 11:37 PM

Thanks for posting the picture. I am sure that there are some who are qualified will evaluate and comment on the condition of lens.


You're welcome. Though having worked with and evaluated professional lenses for nearly 25-yrs, I regard myself as qualified to identify something so conspicuous as failed and flaking coatings. And, as I've said numerous times now, I got a concurring opinion from Tele Vue on this matter when I still owned the eyepiece.

It is what it is. An example of an uncommon issue.

#45 Eddgie

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Posted 14 December 2012 - 09:20 AM

I agree that this picture shows coating flaking off.

The previous picture though looked like a dirty eyepiece.

#46 Starman81

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Posted 14 December 2012 - 11:27 AM

Thanks for the input on the issue that I faced. I had researched CN and found some threads on cleaning with acetone that some of you had also posted in and considered cleaning the 22 Nagler with it. However, reading the precautions about what acetone could do to the eyepiece if not applied very carefully, I resisted, especially because the seller was allowing me to return it. I did not want to take the risk of potentially damaging the eyepiece with any potentially harsher cleaning methods.

With that being said, I found the Nagler 22 an excellent eyepiece (the one night I had it out) and the dirt/grime whatever may have been on the eyepiece did not affect the views in any way that I could tell. On that night, I was able to observe the E and F stars of the Trap for the first time with the 22 in the focuser, I attribute that to the amazingly steady seeing that night but it goes to show that whatever was on that eyepiece couldn't have been holding it back, in terms of performance, much if at all.

#47 Eddgie

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Posted 14 December 2012 - 12:53 PM

The key to using acetone is to be very sparing with it.

Apply it sparingly to a cotton schwab and use light pressure to scrub the spot itself. Be generous with the schwabs. They are cheap.

If you put so much on the schwab that it squeezes out when you touch the glass, you have put to much.

Never apply any cleaner of any kind directly to the lens. The cleaner can be wicked up by the retaining part of the housing and get into the space between lenses.

Only apply to the cloth or schwab, and only a tiny amount. And when it is no longer showing on the glass, get a clean schwab and apply a tiny amount of acetone and go again.

Or, do as you did and just leave it alone.

#48 stevetaylor199

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Posted 14 December 2012 - 02:54 PM

The cleaner can be wicked up by the retaining part of the housing and get into the space between lenses.


Is that the concern involved when using acetone, as mentioned above? Or is there another reason?

#49 Starman81

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Posted 14 December 2012 - 03:20 PM

I also recall reading that it can dissolve plastic and that it is highly flammable.

#50 csrlice12

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Posted 15 December 2012 - 11:12 AM

But you can do your nails AND clean your eyepieces.....






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