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Cleaning primary on a refractor telescope?

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#1 intercept789

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Posted 26 October 2020 - 01:51 PM

Hi, question for people.  I have an Orion long tube 120mm refractor I have had close to 20 years. Nothing special, achromatic, but kinda a good workhorse for viewing planets and such, and still like it. However I wondered if it was my eyes or if indeed the views weren't quite as good.  Looking closely at the primary under lights, it looks like there is a haze on the inside of the glass. I am attaching a photo where bright lights make it pronounced.

 

https://www.dropbox....9[145].jpg?dl=0

 

Should I some how disassemble the refractor to be able to clean the other side of the glass?  I took a quick look at it, and don't see any clear cut way to do this. Anyone have an idea? Is it even an issue? Thanks in advance for advice and suggestions.


Edited by intercept789, 26 October 2020 - 01:51 PM.


#2 lee14

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Posted 26 October 2020 - 02:19 PM

Optics always look worse under bright lighting. That said, if you disassemble the lens assembly to clean it, mark the edges of both elements so they can be reinstalled in the same position. If there are spacers between the lenses, make certain that each returns to its original position. It appears that there is at least one retaining ring securing the lens assembly, and possibly another securing the components together. There are three or four notches in one, smaller round holes in the other. These are gripped by a dedicated tool that will turn the retaining rings to enable disassembly.

 

Lee 



#3 Couder

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Posted 26 October 2020 - 02:23 PM

Mark the lens with a "V" with the point towards the sky, that way you know which way to install it.

Like the picture

Attached Thumbnails

  • Peridier Lens made by Couder (7s).jpg

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#4 MikiSJ

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Posted 26 October 2020 - 02:27 PM

I will second what Lee has posted.

 

If you have a reputable camera repair shop in your area, you might give them a call to see if they do what you need.

 

When I had TAKs, I would always get them cleaned before selling them and the bestest place in the states for that kind of work is "Texas Nautical Repair". This firm knows what they are doing and do it quickly and completely. Not cheap, but if the scope is worth the trouble, these are the folks to go to. Website: https://www.landseaskyco.com


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#5 intercept789

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Posted 26 October 2020 - 03:40 PM

The thing is the scope isn't worth that much.  Is it worth the payoff of taking the time or expense to do?  Not sure.  Brand new the scope would be worth maybe $250, and like I said, it's almost 20 years old. Also since it's not a premium scope, it could be it was constructed to not make disassembly the easiest.  Isn't that how it usually is with cheaper stuff?



#6 Nippon

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Posted 26 October 2020 - 05:19 PM

Personally I would use the clouding to justify a brand new ED120:)


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#7 intercept789

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Posted 26 October 2020 - 09:31 PM

Personally I would use the clouding to justify a brand new ED120:)

Hah...that's on my wishlist but down a bit.  I will get there someday.



#8 Argonautt

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Posted 26 October 2020 - 09:39 PM

There seems to be two holes on the top of the retaining ring made for a tool (lens wrench/spanner) to engage for unscrewing. They're reasonably cheap to acquire if you don't already have one- once that's done, report back what you find underneath.

 

Other than by going in the front I'd ask for more photos- it surely can't be entirely sealed, right?



#9 intercept789

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Posted 27 October 2020 - 09:37 PM

There seems to be two holes on the top of the retaining ring made for a tool (lens wrench/spanner) to engage for unscrewing. They're reasonably cheap to acquire if you don't already have one- once that's done, report back what you find underneath.

 

Other than by going in the front I'd ask for more photos- it surely can't be entirely sealed, right?

I dunno.  Is it worth the hassle and possibly screwing it up?  I have never done anything like this...but I guess I will research it a bit to see if it is doable. I didn't want to force anything, but it seems to be tight, not budging. I think if you are referring to the small holes on the ring, there are actually 3...one cut cut off in photo.  So a "lens wrench/spanner" might take it off, and I would discover what do you think? 




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