15 replies to this topic

[mconnelley]

Hello:

  

  I'm working on cleaning a C11.  It's been sitting in its case for ~8 years and mold has started to grow on the optics.   It's a Fastar compatible unit, so I pulled the secondary first.  It cleaned up beautifully, so I'm optimistic about being able to get the rest of the mold off.  

 

   I then went to pull the corrector plate, and it's stuck.  Naturally I first removed the retaining ring, and that took a lot of 'persuasion' with a dental pick, which I used to pull on the back-side bevel).  After going around a few times, pulling on the back side, the ring finally came loose.  I tried pulling on the secondary mirror housing, and no joy.  I've pulled apart several SCTs before, so I'm used to the plate sticking a bit, but not this much.  I tried with the dental pick again, and was able to get it under the plate and hooked around the back side, but even that didn't get it loose.  I didn't try pulling too hard, and decided to stop and think about it before I broke something.  

 

  Does anyone have suggestions or clever tricks on getting a stuck corrector plate loose?  I could try to simply pull harder.  Given how the corrector is off-center in the lens cell, I can only get the dental pick around 1/4 of the edge of the plate.  I've thought about pressurizing the tube to push it out, but the gap around the edge of the lens would let the air to leak out.  

Cheers

Mike

[WoodyEnd]

I used 99% rubbing alcohol on my stuck C14 corrector and it came right out so be careful it does not hit the floor. I worked over thick towels to be safe.  It did dissolve black ink which ran in streaks over the corrector but that was easy to clean.

 

I should add that I took the cell out first and marked the orientation of the cell and the corrector so that it went back the same way it came out.

Edited by WoodyEnd, 10 May 2018 - 10:25 PM.

[clusterbuster]

Alcohol will work, but BE CAREFUL and don't let the alcohol drip down on the primary, i would lay the ota down horizontally when prying off the corrector plate when using alcohol, it is easier to wipe the alcohol off of the inside of the tube than the main mirror.

Mark

Edited by clusterbuster, 11 May 2018 - 01:03 AM.

[macdonjh]

Alcohol is the standard recommendation for loosening Celestron correctors.  As has been mentioned, don't use a lot, just a drop right at the edge in a few places around the circumference.  Capillary action will wick the alcohol into the space between the glass and the front casting and let it go to work on the sticky stuff.

[rmollise]

Hello:

  

  I'm working on cleaning a C11.  It's been sitting in its case for ~8 years and mold has started to grow on the optics.   It's a Fastar compatible unit, so I pulled the secondary first.  It cleaned up beautifully, so I'm optimistic about being able to get the rest of the mold off.  

 

   I then went to pull the corrector plate, and it's stuck.  Naturally I first removed the retaining ring, and that took a lot of 'persuasion' with a dental pick, which I used to pull on the back-side bevel).  After going around a few times, pulling on the back side, the ring finally came loose.  I tried pulling on the secondary mirror housing, and no joy.  I've pulled apart several SCTs before, so I'm used to the plate sticking a bit, but not this much.  I tried with the dental pick again, and was able to get it under the plate and hooked around the back side, but even that didn't get it loose.  I didn't try pulling too hard, and decided to stop and think about it before I broke something.  

 

  Does anyone have suggestions or clever tricks on getting a stuck corrector plate loose?  I could try to simply pull harder.  Given how the corrector is off-center in the lens cell, I can only get the dental pick around 1/4 of the edge of the plate.  I've thought about pressurizing the tube to push it out, but the gap around the edge of the lens would let the air to leak out.  

Cheers

Mike

 

 

I've encountered this dozens of times. The solution? Gentle prying around the periphery with a wooden manicure stick. Oh, I use a little common tip screwdriver, but I've done this a heck of a lot. Alcohol? That could help in stubborn cases, I guess, but I've never needed such a thing.

 

The only caveat? Don't let the corrector get away from you and break. Pad the area with towels or something else soft.

 

Oh, and if this is an older scope with shims, make sure they go back where they belong.

Edited by rmollise, 11 May 2018 - 10:01 AM.

[Toddeo]

The wooden tool and a hair dryer works. I used a hair dryer to remove a corrector off of a 40 year old sct. It took some time, but it did the trick.

[mconnelley]

Hello:

   

   The alcohol trick worked (used methanol).  It took several iterations of squirt around the edge, wait, pry a little, repeat.  After a while it finally came loose and I have it out and on my desk...in one piece no less!

Cheers

Mike

[gnowellsct]

I used 99% rubbing alcohol on my stuck C14 corrector and it came right out so be careful it does not hit the floor. I worked over thick towels to be safe. It did dissolve black ink which ran in streaks over the corrector but that was easy to clean.

I should add that I took the cell out first and marked the orientation of the cell and the corrector so that it went back the same way it came out.

What he said. The backing cork is blackened with a sharpie or something else that has an adhesive effect. My problem was with a 9.25.

Lay the tube flat on a table so the alcohol (with ink) doesn't drip on to primary. Use an eye dropper to get some alcohol in the crack between corrector and tube. As mentioned a soft towel or something like it is nice to have in front. Before working, remove the fastar if there is one, put a baggie over it with a rubber band to keep out dust and store somewhere safe.

[gnowellsct]

Hello:

The alcohol trick worked (used methanol). It took several iterations of squirt around the edge, wait, pry a little, repeat. After a while it finally came loose and I have it out and on my desk...in one piece no less!

Cheers
Mike

I should have read this first! Good job.

[gnowellsct]

Rod has always recommended prying the corrector, when I encountered the issue I got to be uncomfortable with the leverage I was putting on the corrector plate. I wish Celestron would stop putting that black stuff on. Or maybe they want it to keep the corrector centered during shipping?

[rmollise]

What he said. The backing cork is blackened with a sharpie or something else that has an adhesive effect. My problem was with a 9.25.

Lay the tube flat on a table so the alcohol (with ink) doesn't drip on to primary. Use an eye dropper to get some alcohol in the crack between corrector and tube. As mentioned a soft towel or something like it is nice to have in front. Before working, remove the fastar if there is one, put a baggie over it with a rubber band to keep out dust and store somewhere safe.

 

An OTA doesn't have to have cork, blackened or otherwise, to have this problem problem. I've see this with a wide variety of scopes. What did they all have in common? They were older.

[unitron_man]

Went through this since I discovered my C11 corrector was installed without any shims and very de-centered. 

 

The corrector was in contact with one edge of the cell and a big gap opposite!

 

I could not budge it!.

 

I used a pipe cleaner to absorb some ethyl alcohol and wick it around until it softened the bond.

 

I had the telescope on the mount pointed to the zenith.

 

I carefully pressed around the edge and observed with a flashlight that the bond was wicking in the alcohol.

 

Be patient....

 

When re-installing, I covered the cork with plumbers teflon tape to avoid this getting stuck in the future.

 

I added 8 cork shims around the diameter to center the corrector.

 

 

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[ChapRick]

I just acquired a 10 year old C11 Edge that needs cleaning and the corrector plate is stuck.  So thank you all for your input on this post.  I was not sure what to do and did not want to force it.  

[jkmccarthy]

I used 99% rubbing alcohol on my stuck C14 corrector and it came right out so be careful it does not hit the floor. I worked over thick towels to be safe.  It did dissolve black ink which ran in streaks over the corrector but that was easy to clean.

 

I should add that I took the cell out first and marked the orientation of the cell and the corrector so that it went back the same way it came out.

What he said. The backing cork is blackened with a sharpie or something else that has an adhesive effect. My problem was with a 9.25.

Lay the tube flat on a table so the alcohol (with ink) doesn't drip on to primary. Use an eye dropper to get some alcohol in the crack between corrector and tube. As mentioned a soft towel or something like it is nice to have in front. Before working, remove the fastar if there is one, put a baggie over it with a rubber band to keep out dust and store somewhere safe.

I discovered this thread after an unsuccessful 30+ minutes spent with my new (used; roughly 25 years old) all-off-white C11 recently acquired from Japan, where I believe Vixen sold it as the SC280L [1].  Upon receipt, I successfully collimated it, then next I tackled cleaning the exterior surface of the corrector --- which improved the views somewhat, but the bigger issue was fungus/mold on the corrector's interior-facing surface.  After a diversion ~ 2-weeks ago to work on an 8-inch SCT (which included iteratively clocking its secondary to eliminate a signficant astigmatism problem, then cleaning both sides of the corrector and the secondary mirror, trying to reduced scattered light), I considered myself prepared to remove the C11's corrector plate for cleaning.   However, after discovering (and managing to gently coax off) the stubborn retaining ring, I was not prepared for discovering the corrector plate was solidly stuck to the backing cork, and could not be unstuck with gentle coaxing.

 

Since I'm in Los Angeles, my first thought was to 'punt' and call Celestron (in Torrance, CA, which is not far away) to inquire about bringing it to their service department for evaluation & cleaning.  The person I spoke to said he'd need to consult with others in the service department in the morning (as it was late afternoon when I called, and he wasn't sure if its having returned to SoCal from the Japanese consumer market would introduce any obstacles --- although as far as I'm aware, other than its exterior paint finish it's no different than other C11's of comparable age), and get back to me tomorrow.

 

But based on what I've learned reading this thread just now, I'm currently leaning towards making a second attempt (using a few small drops of alcohol) myself to remove the stuck corrector.

 

Thanks again to all for sharing your collective experiences here !

 

Regards,

 

          -- Jim
_________

 

[1] Just FYI, some photos of the C11 OTA that I bought on-line from a Yahoo! Japan Auctions seller:

 

 

 

"Celestron 11" is clearly embossed on the sky-facing side of the secondary holder, but the SN field underneath is empty.  A label on the tube says "STARBRIGHT COATING" in silver letters on a black background.

[davidc135]

The alcohol drops seem the way to go. Good luck.  David

[jgraham]

Yep, I see this a lot with older SCTs. I apply a little bit of Windex to the rim of the corrector. This seems to penetrate the stuck surfaces and lubricates the cork a bit. After a tiny bit of encouragement with a wooden stick they usually come off easily.