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Cleaning secondary and corrector

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#1 mvandervorst



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Posted 18 April 2016 - 06:21 PM



My N12 has been in an observatory for several years without a lens cap.    Both the secondary and the corrector have crud on them which will not brush off.  Please advise on how best to clean these surfaces.





#2 RamaSpaceShip



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Posted 18 April 2016 - 07:52 PM

Hi Michael,


Put these optical surfaces in warm water (50°C) added with dishwashing liquid. Move them in the liquid until the crud disappears.

Then use isopropyl alcohol to rinse these surfaces, and a hair dryer on cold position to remove the alcohol..


Then you can put them back, cleaned!!!


(This works also for the main mirror.)


Best regards.



#3 GeorgeCarey



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Posted 19 April 2016 - 07:13 PM

Some optical surfaces that I have cleaned have stubbornly refused to come clean with isopropyl alcohol.
I now finish the cleaning by breathing on the surface and carefully wiping with a soft tissue.
It seems to work well.

ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk

#4 MarkS



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Posted 20 April 2016 - 03:12 AM

 If I use detergent I make a very dilute solution in distilled water - much less than than you would use for dishwashing - using a fragrance free detergent. Then I rinse MANY times with distilled water - It is amazing how many rinses you need to get rid of the residue!


For very stubborn spots I use a lens cleaning solution from VisibleDust, applied with a very soft microfibre cloth, with a very gentle wiping action - but only after all loose dust has been removed



Edited by MarkS, 20 April 2016 - 03:14 AM.

#5 mvandervorst



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Posted 21 April 2016 - 06:54 AM

Thanks guys,


Now for the scary part, doing it.

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