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Eyepiece maintenance KOWA 50x Wide (1 Viewer)

yves0071

Well-known member
Hi
I have an eyepiece KOWA 50x Wide (from 820 series) which requires cleaning (dust inside on the internal top lense).
How to open it? I removed the rubber eyecup and I already unscrew the top but cannot get access to the internal lense.
Any advice is welcome :)
Thanks in advance
Yves
 

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Tringa45

Well-known member
Europe
Yves,

If it's just a little dust it will not have any noticeable effect on the image quality.
To clean the eyepiece yourself you would need special tools to disassemble it, and might then have problems geting all the lens elements back together in the right order.
If you still consider it necessary to have the eyepiece cleaned, then it would have to be done by a professional camera/optics service.

John
 

dipped

Well-known member
Hi
I have an eyepiece KOWA 50x Wide (from 820 series) which requires cleaning (dust inside on the internal top lense).
How to open it? I removed the rubber eyecup and I already unscrew the top but cannot get access to the internal lense.
Any advice is welcome :)
Thanks in advance
Yves
It looks like the top plate will unscrew if you use a tool akin to nose pliers in those two little holes opposite each other.
 

jring

Well-known member
Hi,

cannot comment on this EP but have a general word of warning - lenses in eyepieces are often just stacked into the tube (with spacers where needed) and held by a single retainer. So opening the EP and then turning it around makes the whole stack fall out and good luck getting it back together in the proper order.

For added fun, on some astro EPs the retainer is actually the 1.25" barrel... so people wanted to unscrew the barrel and transformed their expensive Nagler into a heap of lenses... Televue support loves those cases - and usually can help people to get them back together...

The correct way to do it is to firmly seat the EP on a round holder which is smaller than the tube diameter, then unscrew the retainer and carefully slide the tube down so the stack keeps in one. Then you can check if the lenses are held together with tape or not, if there are markings for the correct order (the traditional optician way to do this is to mark the whole stack with a V with the point to the objective aperture or field lens - usually only in pencil on the ground lens edges).
If there are no markings, make your own!

If there are multiple spacer rings, they are probably of different thickness so take care to get them back in in the right position.

If you see lenses spaced in the traditional way with pieces of tinfoil, best keep away and let a pro do it... although that is usually the case with objective lenses.
If you must work on sth spaced with tinfoil, extra care must be taken to document the position of the spacers and lenses to get them back together exactly as they were as these spacers can be and are used to correct various aberrations from lens manufacturing (ususally wedge).

Good luck,

Joachim
 

yves0071

Well-known member
Dear Colleagues,
Thanks for your feed back and usefull advices.
I have unscrewed teh top using the 2 holes but it is only a cover. Cannot remove the lense.
Best regards
Yves
 

jring

Well-known member
Hi,

I just did a bit of surgery on my old 60x small body EP - when I unscrewed the top cover I got a loose eyelens... which I didn't dare to remove as I had not marked the up side...

But on the bayonet mount side there is another retainer with different fastening mechanism (slits instead of holes) - I guess the lower part is accessible from there and we don't have a single stack of glass... but rather the eyelens (and maybe more) comes off from above and the field lens (and maybe more) from below... once again be careful not to get a stack of unsorted lenses and retainers...

Joachim
 

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