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Recementing a 3" Achromatic objective

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#1 Valmigo

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Posted 04 May 2021 - 04:13 PM

Does anyone know of an optical company that can do this job?



#2 photoracer18

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Posted 04 May 2021 - 04:40 PM

I know there are companies that do it because the previous owner of my TMB 80 SS triplet had it fixed from the same problem. He never told me the company's name but said it was a larger well known optical company.



#3 siriusandthepup

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Posted 04 May 2021 - 05:06 PM

Cemented objective issues

 

From CN. Not an impossible job for a patient person. Does not cost much to do it either.



#4 RichA

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Posted 04 May 2021 - 05:21 PM

For the heck of it, could always try air-spacing in the interim.



#5 BGRE

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Posted 04 May 2021 - 05:52 PM

If using UV cured adhesive such as NOA61 its important that UV illumination non uniformity across the adhesive layer be less than 10% or measurable aberrations due to index gradients etc within the cured adhesive layer will occur. Similar non uniformities when using optical epoxies can also occur if the epoxy is left on the first element for more than a few seconds before the second element makes contact.:

https://www.research...ic_applications



#6 Steve Dodds

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Posted 04 May 2021 - 06:00 PM

You could probably just put it out in the Sun.



#7 ccaissie

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Posted 05 May 2021 - 07:25 AM

De-cementing it is probably the crux.  You could air space it, or oil it.  Usually 3" is a practical limit for cementing.  We have a 4" triplet made by Stan Brower...found it in a junk box.  It star tests horribly...big astigmatism, the cementing has bubbles/voids.  One of our members got excited at the find and started a formal build, cell, focuser.   I slapped together a tube to test it out, and it has now never been in use.

 

It would be interesting to de-cement it and redo it.  It hasn't come up near the top of anyone's  "to do" list.  Older Balsam cemented lenses come apart with heat and solvent...I have no idea how to de-cement something with the newer polymer cements.



#8 DAVIDG

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Posted 05 May 2021 - 08:53 AM

 I have done it many times, here is a  link to my thread on  how I typically  do it  https://www.cloudyni...ecement-a-lens/

 

                         - Dave 


Edited by DAVIDG, 05 May 2021 - 09:18 AM.


#9 BGRE

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Posted 05 May 2021 - 09:03 AM

A report by Leica for ESA on optical cements for space applications:

http://emits.sso.esa...FinalReport.pdf

Includes method used for precision centering that doesn't rely on accurate lens edging.

Also indicates why collimated UV is desirable for curing  etc.




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