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Is my corrector ruined? 1969 3.5 standard DIY service woes

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#1 iflyforfood

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Posted 31 July 2020 - 05:21 PM

New member shout out to Ben for referring me here.

 

While waiting on my primary mirror to come back from majestic I was trying to clean some haze on the inside of the corrector which looked like it had the same haze you get on your cars interior windshield from the off-gassing of the plastics/sunshade and what not.

 

Well turns out even after using distilled water, brand new pec pads, gloves and as much gentleness I could muster it's now much worse. Are the coatings just old and ruined at this point? (they certainly were for the primary). I also did this in-situ thinking I'd only remove it all if I felt I really needed to get something out of the far edges.

 

I called Cumberland earlier this week in as I figured I may as well recoat this too as well and they said that they "do not provide recoating services to questar end users" point blank. Which is contrary to what I've read here and what I've been told so I'm very much confused. 

 

At any rate, what am I to do aside from banging my head against a wall?

 

Pics:

IMG 20200731 164422
Album: hazy corrector
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Edited by iflyforfood, 31 July 2020 - 05:22 PM.


#2 davidmcgo

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Posted 31 July 2020 - 07:30 PM

I would take the corrector out and wipe down the inside surface with acetone.  Just don’t get any on the painted spot on the outer surface.

The retainer for the corrector has a few glue spots that will need StarBond cyanoacrylate remover to free up before you can unscrew.

 

Dave


Edited by davidmcgo, 31 July 2020 - 07:31 PM.

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#3 DAVIDG

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Posted 31 July 2020 - 07:33 PM

Did you have Broad Band coating or standard ones. If they are standard coating then they are MgF2. The coating on my 1961 Questar was hazy as well. Cumberland did a great job on my  corrector but that was a couple of years ago when the sons of the original owner were running Cumberland. When I called them one of the sons answered and said he would be happy to recoat it and when I called when I got it back to thank them the son said he was pleased to see his Dad's hand writing on the side and told me that it was made in March of 1961 from looking it up  in their records. I understand that the sons retired and sold the company. So maybe Cumberland is no longer recoating the optics. If so that is too bad because if one had the skills to remove the optics they could be recoated for few hundred dollars and keep the scope original vs sending it back to Questar and having them replaced for I believe $1500 or more.  

 

            - Dave 



#4 iflyforfood

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Posted 31 July 2020 - 08:02 PM

I would take the corrector out and wipe down the inside surface with acetone.  Just don’t get any on the painted spot on the outer surface.

The retainer for the corrector has a few glue spots that will need StarBond cyanoacrylate remover to free up before you can unscrew.

 

Dave

 

I'll give that a shot. Is it safe to let the acetone touch the secondary mirror? Acetone also dissolves CA glue pretty well in my experience from RC planes.

 

edit: giving up with giving it a shot. Soaked the 4 glued corners of the ring with as much acetone it would take without spilling into the lens. Ended up doing the whole circumference. I could not get it to budge for the life of me. Quit trying to get it lose for fear of destroying it. The one notch on the ring kept slipping on the tool so it's rounded out a bit now so it's just getting worse the more I try so I'm gonna stop there. Also a drop or 2 of acetone got on the outer edge of the lens and the spots are severely hazed now. It's an old jug of acetone so it's probably not too clean.

 

Did you have Broad Band coating or standard ones. If they are standard coating then they are MgF2. The coating on my 1961 Questar was hazy as well. Cumberland did a great job on my  corrector but that was a couple of years ago when the sons of the original owner were running Cumberland. When I called them one of the sons answered and said he would be happy to recoat it and when I called when I got it back to thank them the son said he was pleased to see his Dad's hand writing on the side and told me that it was made in March of 1961 from looking it up  in their records. I understand that the sons retired and sold the company. So maybe Cumberland is no longer recoating the optics. If so that is too bad because if one had the skills to remove the optics they could be recoated for few hundred dollars and keep the scope original vs sending it back to Questar and having them replaced for I believe $1500 or more.  

 

            - Dave 

Standard vanilla un-fancy coatings. I guess I'm too late for cumberland to bother with us anymore. Are there any other alternatives since majestic cant do these correctors?


Edited by iflyforfood, 31 July 2020 - 09:17 PM.


#5 davidmcgo

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Posted 01 August 2020 - 04:03 AM

The StarBond debonder evaporates much slower than acetone so order that and give it another try.

 

Dave



#6 iflyforfood

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Posted 01 August 2020 - 07:45 AM

The StarBond debonder evaporates much slower than acetone so order that and give it another try.

 

Dave

Makes sense, will do.



#7 Mike Allen

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Posted 01 August 2020 - 08:29 AM

It’s time to go missed approach and send it to Questar.


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#8 DAVIDG

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Posted 01 August 2020 - 10:32 AM

    On mine I took a razor blade and carefully cut through the two areas were  I could see were the glue was applied and the ring came loose. I have restored many optical decides and if the retainer ring doesn't easily unscrew, it is time to get out the heat gun and heat it up 

   Majestic  will apply MgF2  but they don't strip the old coating and I don't believe they have the mask to apply the secondary spot again. 

   There are a couple of materials that will strip MgF2, concentrated warm to hot critic acid ie lemon juice, hot sulfuric acid and oxaltic acid. If it has the aluminized spot on the front of the corrector then the front surface can be protected and the coating strip off the back surface. 

   It is a shame that Cumberland won't work with Q owners any longer. If you send your scope back to Questar they are going to replace the optics and the cost be close what you can find a used one for. 

 

                - Dave 


Edited by DAVIDG, 01 August 2020 - 11:23 AM.


#9 Gregory Gross

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Posted 01 August 2020 - 11:29 AM

Perhaps a call to Questar next week is in order to confirm this, but, based on the way this thread reads, it sounds like Cumberland by way of Questar will no longer recoat optics. That is, the recoat option is no longer available even if you go through Questar, and an outright replacement of the optics set (corrector and primary mirror, since they’re matched) is the only option. Is this right? My gut says this doesn’t sound accurate.



#10 iflyforfood

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Posted 01 August 2020 - 12:34 PM

It’s time to go missed approach and send it to Questar.

I'm about to leave the holding pattern direct.

 

    On mine I took a razor blade and carefully cut through the two areas were  I could see were the glue was applied and the ring came loose. I have restored many optical decides and if the retainer ring doesn't easily unscrew, it is time to get out the heat gun and heat it up 

   Majestic  will apply MgF2  but they don't strip the old coating and I don't believe they have the mask to apply the secondary spot again. 

   There are a couple of materials that will strip MgF2, concentrated warm to hot critic acid ie lemon juice, hot sulfuric acid and oxaltic acid. If it has the aluminized spot on the front of the corrector then the front surface can be protected and the coating strip off the back surface. 

   It is a shame that Cumberland won't work with Q owners any longer. If you send your scope back to Questar they are going to replace the optics and the cost be close what you can find a used one for. 

 

                - Dave 

I'll have to call Questar I guess and see what they say. I'll try the heat trick.

 

Perhaps a call to Questar next week is in order to confirm this, but, based on the way this thread reads, it sounds like Cumberland by way of Questar will no longer recoat optics. That is, the recoat option is no longer available even if you go through Questar, and an outright replacement of the optics set (corrector and primary mirror, since they’re matched) is the only option. Is this right? My gut says this doesn’t sound accurate.

From what Cumberland told me they want me to go straight to Questar. I'll give them a ring Monday



#11 Optics Patent

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Posted 01 August 2020 - 01:51 PM

The Cumberland balk is a surprise. They have coated for me in the past year. Try again. I have seen lots of price variability from them so this could be treated as a “Not right now”.

#12 iflyforfood

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Posted 01 August 2020 - 01:54 PM

The Cumberland balk is a surprise. They have coated for me in the past year. Try again. I have seen lots of price variability from them so this could be treated as a “Not right now”.

Maybe I'll have a lady friend call them with a sultry voice  see if they change their tune lol.gif​ 



#13 alwilder

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Posted 01 August 2020 - 04:18 PM

JR Cumberland is located in Marlow Heights, MD and according to their website is currently owned by 2 employees that have worked there for 25-30 yrs. One option to try is contacting Company Seven in nearby Laurel MD to see if they can provide any guidance since they sell Questars and various other high end telescopes. Worst case scenario is to sell your scope for parts only and use the money for another Questar or possibly a different scope like a medium focal ratio apo refractor. No scope is perfect and while Questars are fine instruments they have their limitations being a highly compact but slow focal ratio scope that's ideal for terrestrial, lunar, planetary and binary star observation.


Edited by alwilder, 01 August 2020 - 04:19 PM.

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#14 iflyforfood

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Posted 01 August 2020 - 04:28 PM

Worst case scenario is to sell your scope for parts only and use the money for another Questar or possibly a different scope like a medium focal ratio apo refractor.

It's family heirloom I inherited from grandfather and I'll probably be lynched by the rest of my family if I got rid of it. If this ends up being its demise then I'll have to relegate it to display duties until I can actually throw away money at it for all new optics. I only use it very occasionally. An ETX 125 is within my budget though so I may just settle with one of those for actual use.


Edited by iflyforfood, 01 August 2020 - 04:30 PM.


#15 dan boyar

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Posted 02 August 2020 - 10:41 PM

I would stay away from acetone.  It will not cut oils, grease or wax.  Dishwashing liquid and water swabbed gently with a paper towel then rinse with distilled water.  Let drain and dry and then blot dry and remaining droplets with paper towel.  That should remove any greasy film residue and not cause any harm.  Good luck...



#16 Optics Patent

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Posted 03 August 2020 - 06:42 AM

My go-to lens cleaner (if ethanol or methanol don't do the trick) is butane lighter fluid.



#17 iflyforfood

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Posted 03 August 2020 - 08:29 AM

I've yet to still be able to remove the corrector from the tube, I have starbond on order. But I'll try those other fluids in situ.


Edited by iflyforfood, 03 August 2020 - 09:03 AM.


#18 DAVIDG

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Posted 03 August 2020 - 08:59 AM

 It looks to me that the MgF2 has deteriorated.  It happened to my corrector.  If  that is the case your  not going to clean the haze off with an organic solvent. If  the haze was organic like out gassing from the paint it would come off with acetone, or  an organic alcohol like methanol or ethanol ( I'm research chemist and engineer and have been making optics for 35+ years now)    The MgF2 needs to be stripped with an acid solution or mechanically polished off but mechanical polishing will change the optical figure and the corrector will need  to be refigured.  So you have to be careful if you rub on the surface to remove the coating because you can make the optical figure  lumpy. 

 

                      - Dave 



#19 iflyforfood

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Posted 03 August 2020 - 09:04 AM

 It looks to me that the MgF2 has deteriorated.  It happened to my corrector.  If  that is the case your  not going to clean the haze off with an organic solvent. If  the haze was organic like out gassing from the paint it would come off with acetone, or  an organic alcohol like methanol or ethanol ( I'm research chemist and engineer and have been making optics for 35+ years now)    The MgF2 needs to be stripped with an acid solution or mechanically polished off but mechanical polishing will change the optical figure and the corrector will need  to be refigured.  So you have to be careful if you rub on the surface to remove the coating because you can make the optical figure  lumpy. 

 

                      - Dave 

I meant I haven't been able to remove the corrector from the tube. But if worse comes to worse if Everclear doesn't work (next thing I'll try), would vinegar work for removing the coating?



#20 DAVIDG

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Posted 03 August 2020 - 11:22 AM

 No vinegar won't work.  You need to react MgF2  with an  acid to make a water soluble compound.  Strong Critic acid is the safest thing to try, ie concentrated lemon juice  you can get at the grocery store.  You may need  to do it warm to hot and let it soak.   Is  the  hazy on the coating  on the top surface and your secondary spot is located on the rear surface ? If so they you can protect the rear surface while trying. Did  you get the mirror back from Majestic ? If so how does it look ?  What  is the serial number of your Questar ?

 

                     - Dave 



#21 iflyforfood

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Posted 03 August 2020 - 11:44 AM

 No vinegar won't work.  You need to react MgF2  with an  acid to make a water soluble compound.  Strong Critic acid is the safest thing to try, ie concentrated lemon juice  you can get at the grocery store.  You may need  to do it warm to hot and let it soak.   Is  the  hazy on the coating  on the top surface and your secondary spot is located on the rear surface ? If so they you can protect the rear surface while trying. Did  you get the mirror back from Majestic ? If so how does it look ?  What  is the serial number of your Questar ?

 

                     - Dave 

I would've figured plain acetic acid/white vinegar might work but I do have a bottle of lemon concentrate from costco. The haze is on the rear surface as is the secondary. 

 

It was just delivered to majestic today so hopefully ill get the primary back by the end of the week.

 

#9-3746


Edited by iflyforfood, 03 August 2020 - 11:47 AM.


#22 DAVIDG

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Posted 03 August 2020 - 12:20 PM

 The problem is that the secondary spot is on the rear and any acid is going to take it off as well unless it is well protected.  What did the mirror look like that it also needed to be recoated ? 

   Mine wasn't as bad as yours but it was hazy. I called Questar and they told me the MgF2 had gone bad and they had seen it many times. They wanted me to send it in and they would replace the optics for around $1500.  They said they don't recoat just replace. That is when I called Cumberland to ask their  advice and person answering the phone said he would be happy to recoat but I would need to reapply the paint over the spot. I choose to buy the modern aluminium disk and apply it myself.  Maybe because I have a pretty good understanding of optics and that may have come across in our conservation that Cumberland agreed to recoat?  Maybe they now have an agreement with Questar not to do any work on them or maybe it is just to much of bother or they can't guaranty the results ?  Hopefully Cumberland will change their mind since it easy for them to strip it, apply MgF2 to both the front and the back since it might not have it on the front surface and then apply secondary spot. 

 

           - Dave 



#23 iflyforfood

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Posted 03 August 2020 - 12:37 PM

 The problem is that the secondary spot is on the rear and any acid is going to take it off as well unless it is well protected.  What did the mirror look like that it also needed to be recoated ? 

   Mine wasn't as bad as yours but it was hazy. I called Questar and they told me the MgF2 had gone bad and they had seen it many times. They wanted me to send it in and they would replace the optics for around $1500.  They said they don't recoat just replace. That is when I called Cumberland to ask their  advice and person answering the phone said he would be happy to recoat but I would need to reapply the paint over the spot. I choose to buy the modern aluminium disk and apply it myself.  Maybe because I have a pretty good understanding of optics and that may have come across in our conservation that Cumberland agreed to recoat?  Maybe they now have an agreement with Questar not to do any work on them or maybe it is just to much of bother or they can't guaranty the results ?  Hopefully Cumberland will change their mind since it easy for them to strip it, apply MgF2 to both the front and the back since it might not have it on the front surface and then apply secondary spot. 

 

           - Dave 

Upon closer inspection the mirror is actually in the front surface.



#24 alwilder

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Posted 03 August 2020 - 01:24 PM

The views pictured of the hazy spot are from a fairly oblique angle, so how bad does it look straight on or just a slight angle of a just few degrees? Possibly when the recoated mirror is returned and the scope is put back together, actual testing on in the field may yield results better than expected. Having an idea of how the scope performed prior to service will let you know if recoating the corrector optics is worth the money once the mirror is re-installed. I know nothing about the durability of  Cumberland's1969 coatings but I would hope they'd be reasonably durable assuming the scope was well cared for and not exposed to high humidity (fungus risk) or extreme temperature fluctuations (outgassing risk). Coatings can be weird depending on the manufacturer or inadvertent damage from improper cleaning. For example Nikon coated rangefinder lenses from the early 1950s were very durable and still hold up well today while the better Leica rangefinder lenses had softer coating from the same period that were prone to degradation and haze prior to the late 1960s when their coatings were more robust.



#25 iflyforfood

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Posted 03 August 2020 - 02:25 PM

The views pictured of the hazy spot are from a fairly oblique angle, so how bad does it look straight on or just a slight angle of a just few degrees? Possibly when the recoated mirror is returned and the scope is put back together, actual testing on in the field may yield results better than expected. Having an idea of how the scope performed prior to service will let you know if recoating the corrector optics is worth the money once the mirror is re-installed. I know nothing about the durability of  Cumberland's1969 coatings but I would hope they'd be reasonably durable assuming the scope was well cared for and not exposed to high humidity (fungus risk) or extreme temperature fluctuations (outgassing risk). Coatings can be weird depending on the manufacturer or inadvertent damage from improper cleaning. For example Nikon coated rangefinder lenses from the early 1950s were very durable and still hold up well today while the better Leica rangefinder lenses had softer coating from the same period that were prone to degradation and haze prior to the late 1960s when their coatings were more robust.

You can see it from any angle as long as I shine a flashlight through the rear of the tube. Otherwise it's not terribly obvious. 




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