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Time to clean the corrector plate

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#1 Electronchuck

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Posted 21 June 2021 - 07:55 AM

I have a Celestar 8 from about 2000 with Starbright coatings and need to clean the surface of the corrector using the recommended techniques. Does anyone know if those coatings are more easily damaged that the current Celestron coatings? I assume they are all mostly MgF.

#2 ngc7319_20

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Posted 21 June 2021 - 08:48 AM

Never had a problem cleaning StarBrite coatings on Celestrons from the era...  If you have some doubts, just clean a small area and inspect, before taking on the entire corrector.



#3 lattitrail

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Posted 21 June 2021 - 09:00 AM

My first telescope was a Celestron 9.25 of the same vintage. I can say from experience that tightening the retaining screws too much will result in a cracked corrector plate. I thought I had barely snugged them down after removing it for the first clean but apparently it was too tight to allow the glass to expand or contract with changing temperature. It was still in one piece when I put it away but cracked all the way across when I retrieved it the next evening. Hopefully you can avoid making the same mistake I made years ago.  



#4 Electronchuck

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Posted 21 June 2021 - 11:56 AM

Thanks everyone. I'm just cleaning the outside of the corrector so I don't plan to remove it.

#5 choward94002

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Posted 21 June 2021 - 12:22 PM

As with all glass, use the "puff puff dab toss dab toss" technique ... get a lens puffer, a small USB fan, a box of unscented cotton balls, some gloves and a microfiber towel.  Make up a cleaning solution depending on what you're trying to clean off (lot's of threads here about that, or ask) and clear out a few hours from your schedule ...

 

With a corrector plate it's important that no moisture get into the OTA interior, so you will need to clean it inverted (so that the scope is pointed plate down) ... here's what I do:

 

Set the fan so that it blows across the corrector (pointed down), I will also usually take a small flashlight with a clip on it and shine it across the corrector plate to see any areas that need work.  Start puffing directly vertical to the plate, spiral pattern, inside going out, two rep's ... that is basically knocking loose any dust particles from the plate and keeping them from resettling ... "puff puff" ...

 

Once that's done then it's time to "dab toss dab toss" ... put on your gloves, get a cotton ball, dab it into the solution (you want it damp, not soggy), dab it on the microfiber (to take off excess), start in the center next to the secondary and dab (slight pressure) up and down on a spot on the corrector.  Toss the ball and repeat (about a few thousand times), three rep's spiral pattern ...

 

Last pass will be with distilled water, same thing ... "dab toss dab toss dab toss" ... it can be almost zen like, think Karate Kid with wax on/ wax off ... :)




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