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Old 09-01-2025, 07:32 PM
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tempestwizz (Brian)
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Issue with Tak Hi LE-3.6mm

I purchased this eyepiece new from Claude at AEC some 12 or so years ago, but it has very little use as a high end view piece. Most of its use time was as a fine tune centring eyepiece to synchronise the positions of stars for my ArgoNavis alignment, and focus was rarely sought, as the out of focus star circle allowed easy centring for the AN.
More recently, I have brought out the Tak lens to engage in some planetary viewing and I have to say I was not terribly impressed with the views. Initially I put it down to the terrible seeing conditions experienced in Laos where high cloud usually stymies any serious viewing.
My OTAs have been a Tak Toa130 and my 18” F3.5 dob.
However doing some cloudy night fiddling around I had a critical look at the Tak lens, and note that the top element is not clean. While there is the usual dust on the external surfaces, I see a fungus type growth on the underside of the top piece of glass. That should have been sealed at manufacture and be pristine on the inside; irregardless of the age of the lens.
The lower elements of the eyepiece are fine.
I guess the eyepiece is well out of warranty, but I feel it should not have ever happened.
Something for users considering a Tak lens purchase.
Hopefully the attached photos will display to others what I am seeing here.

First photo shows lens ID, 2nd shows top surface of top element, and final two show under surface of top element.

Cheers Brian Clements
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Last edited by tempestwizz; 09-01-2025 at 07:39 PM. Reason: Spelling error in headline
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  #2  
Old 09-01-2025, 07:58 PM
Rainmaker (Matt)
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Hello Brian,
I doubt that there are very many eyepieces that are sealed well enough to prevent fungal attack in Laotian climate. I previously bought a Vixen LV that had a similar affliction of fungal infestation, I dismantled it, making sure every not to mess up the order of elements, and washed the affected surfaces in isopropyl alcohol…… worked perfectly ever since.
Expose the eyepiece to lots of UV light to make sure that it doesn’t grow back…
Even here in Canberra’s dry conditions, one has to allow all dew to evaporate prior to storing optics.

Cheers,

Last edited by Rainmaker; 09-01-2025 at 08:14 PM.
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  #3  
Old 09-01-2025, 08:21 PM
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tempestwizz (Brian)
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Hi Matt, thanks for the response. The Tak lens is a bit finicky getting to the upper elements. Need to access via the bottom. I will need to fabricate a special tool to engage the retaining collar methinks. Have to sleep on that one! I’ll be travelling for the next couple of months so it can wait til mid year when the seeing here is permanent rubbish.
(As an aside, I’m impressed with your Excalibur build. My build version with Mark’s mirror is reasonably functional, but not without its flaws. The 18” does gather a reasonable amount of light to cut through the soupy skies here though.)
Cheers Brian
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Old 09-01-2025, 08:41 PM
Wilso
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Some eyepieces and binoculars are nitrogen purged for waterproofing, to prevent moisture and dust from entering. These are more likely hiking and spotting scope equipment, some astronomy eyepieces. Who knows how long they would last in a high humidity environment though .Good luck cleaning and rebuilding your eyepiece
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Old 09-01-2025, 11:34 PM
Leo.G (Leo)
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While sunlight and UV lights will apparently help reduce or prevent future fungal growth and kill what's there, if it's only surface fungus and not etched into the glass and I can safely disassemble the unit without mixing the order of glass I have for many years used white vinegar on camera lenses and telescope lenses, rinsed very well with fresh distilled water after the vinegar wash. It has served me well for several years but in saying that my entire OTA's are probably worth less than that one Tac eyepiece.
I had a problem many years ago with a near new Nikon 80-200 f2.8 ED lens which I'd kept stored in it's leather canister type case. I had no idea the case was only for travel not storage, it was an expensive lens and was left in a slightly damp room. That went to a professional down in Rockdale, NSW (Peter someone, old Austrian fellow from memory and very smart) back in the early to mid 90s for a full strip and clean and by the grace of photography deities the fungus hadn't marked the lens with any etching, it's never happened again and the repair was far from cheap as was the lens (on my then wages) purchased new in 91
I am however grateful I don't live in a climate with monsoons and humidity I could only guess Vietnam has. I'm also a lot more careful with lens storage now..


Quote:
Originally Posted by Wilso
Some eyepieces and binoculars are nitrogen purged for waterproofing, to prevent moisture and dust from entering

A question for those in the know, I've seen eyepieces listed as such but is it a process that has to be reapplied after some time as o-rings deteriorate or do they go in the bin and you buy new units?


Is this the same procedure applied to expensive APO lens assemblies or am I getting confused with oil which can eventually leak out?
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Old 10-01-2025, 09:52 PM
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tempestwizz (Brian)
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Further to the Tak lens issue:
I fabricated a suitable tool to allow removal of the upper element cluster.
This revealed that the upper elements consist of a triplet cemented together, and a fourth air spaced element.
Cleaning the triplet and the single element did not improve anything, as the grunge can be seen within the triplet. There is no way for dis assembly of the triplet. I call it grunge, as with the ability to view the triplet closely by itself, my issue is not fungus, but what appears to be congealed oil between the triplet elements.
It would be difficult to convince me that this is the result of environmental conditions, or variations in ambient humidity, as the triplet is clearly sealed around its edges with black paint.
Maybe it’s an age issue where the oil has deteriorated over time, but - what lifetime should one be able to expect from such a purported high quality lens?
It brings me back to my original suggestion that current and prospective owners of this type of lens should look VERY closely at them. A casual scan at the lens does not reveal anything, it’s only when you look closely. For me, most of the time, the lenses were/are kept in the lens case, which is usually only opened in the dark when I want to view. Through the lens, the fault shows as ghosting or a halo around the subject rather than a crisp clean image.
For my part, I won’t be buying any more Tak lenses.

Cheers, Brian
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Old 10-01-2025, 11:31 PM
Leo.G (Leo)
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Quote:
Originally Posted by tempestwizz
Cleaning the triplet and the single element did not improve anything, as the grunge can be seen within the triplet. There is no way for disassembly of the triplet. I call it grunge, as with the ability to view the triplet closely by itself, my issue is not fungus, but what appears to be congealed oil between the triplet elements.

If the element isn't bonded and is held with oil there would be a suitable product you could soak it in the eventually separate the elements. I'm not too sure how complex it would be to replace the oil as it isn't just 15w30 motor oil (or is it?) from the mechanical supply, I honestly wouldn't know what oil it is.
Were you to do some research/have someone here with the knowledge provide the correct information it may be well recoverable.

I would assume there is a set orientation where both glass elements should mate up and perhaps some sort of mark on the edge that wouldn't dissolve would ensure proper orientation should you attempt the repair.



If it's oil the elements wouldn't be bonded as such, old oil becomes like glue I don't believe they are physically bonded (based on what I've read about triplets with oil), it would more be a stiction thing. Were there anyone locally experienced in the procedure it could be worth checking into having dome professionally for a high quality eyepiece.
I'll do a search tomorrow and see if I can find any information.
The oil in the triplets does occasionally have to be replaced from something I read some time back, maybe not always, some are apparently very good over the life time but I have seen mention of oil filed lens cells leaking when the o-rings perish with age.
I'm sorry, as mentioned, I don't get to play with any luxury type equipment so I have no experience but I do know how to do research and if I can find anything out I'll let you know.
I have the time to search but tomorrow, bed time now.
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Old 11-01-2025, 06:41 AM
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It is, unfortunately, the failure of the glue between the elements of the triplet. This occurs often and there are threads on cloudynights.com about it.
It is especially common with elements glued together by Balsam cement.
You can research how to unglue and then re-glue the elements, or simply chalk this up to experience and the "school of hard knocks".
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Old 11-01-2025, 11:42 AM
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tempestwizz (Brian)
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Thanks for the input guys. It is of some small comfort to find out I’m not Robinson Crusoe in this. I will consider my options. I have nothing to lose, and so will probably attempt disassembly at some point when I’ve nothing else requiring my attention.
Cheers, Brian
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Old 11-01-2025, 03:28 PM
Leo.G (Leo)
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Brian I restore a few Nikon lenses I've managed to pick up extremely cheap because they have a stuck mechanism or minor fungi. Normally in a price range I couldn't afford but if I can score them for around $50 I can afford to take the risk and strip them down. I've acquired some very good lenses this way and gotten them working (I'm poor not cheap). One still has minor fungal intrusion because it is between the glued elements and I wasn't game to go that far with the destructive cleaning but it's not visible in images and the lens performs well. A couple had stuck zoom mechanisms, one was loose screws and a very easy fix after a full strip down of mechanisms but information isn't always impossible to find and my son has good eyes and is smart (I have poor eyesight) and can see the tiny stuff I can't see (though I will put up to 4 pairs of reading glasses on if necessary to see, mainly doing electronics). I do have good help with the younger eyes.
If the eyepiece is not of usable quality as it is and it's long been paid for and not valuable to sell in it's current condition it boils down to having little to lose and valuable experience to gain (even if just for your own benefit) but do search for instructions for a higher chance of success.
Be careful which order the glass is laid out in if multiple elements. I had one camera lens (old Pronto lens from non functional Zeiss) and as I tried to put one element back in I dropped it and had no idea which way it went. Since I'll never use the camera and it just goes in my collection, while annoyed with myself it's not of major importance but I'd rather not have those problems and get everything right. Otherwise the rest of the complex lens mechanism is now working, it wasn't when I obtained the camera.
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Old 11-01-2025, 10:18 PM
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tempestwizz (Brian)
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Thanks for the advice Leo, I’ll bear that in mind. Cheers
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