Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Issues with my primary mirror cleaning

  • Please log in to reply
7 replies to this topic

#1 Miksubi

Miksubi

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 09 Dec 2023

Posted 10 December 2023 - 02:16 AM

Might be a dumb question, but how would I know if I've rubbed off the coating on my primary mirror? Got my first telescope recently, and it was fairly dirty so I decided to clean it. Did it according to how a few videos described plus what the instructions said (Distilled water, dawn dish soap, capful of rubbing alcohol, cotton balls/fingertip method.) After doing so, when the mirror was dry I noticed it had blue and gold/green hues all throughout, and was still blurry. I figured it would need a re-coating anyway so i decided to use straight rubbing alcohol and cotton, a microfiber towel and a good bit of pressure to try and rub this blueish gold film off, and surprisingly it worked, it took it off and in the end the mirror seems far cleaner. But now I'm worried if i took a coating off and if theres a chance of rust with the aluminized mirror? Again, Im new to telescopes and have very little knowledge. The scope is a used Orion XT10.

#2 Keith Rivich

Keith Rivich

    Fly Me to the Moon

  • *****
  • Posts: 6,805
  • Joined: 17 Jun 2011
  • Loc: Cypress, Tx

Posted 10 December 2023 - 02:38 AM

Might be a dumb question, but how would I know if I've rubbed off the coating on my primary mirror? Got my first telescope recently, and it was fairly dirty so I decided to clean it. Did it according to how a few videos described plus what the instructions said (Distilled water, dawn dish soap, capful of rubbing alcohol, cotton balls/fingertip method.) After doing so, when the mirror was dry I noticed it had blue and gold/green hues all throughout, and was still blurry. I figured it would need a re-coating anyway so i decided to use straight rubbing alcohol and cotton, a microfiber towel and a good bit of pressure to try and rub this blueish gold film off, and surprisingly it worked, it took it off and in the end the mirror seems far cleaner. But now I'm worried if i took a coating off and if theres a chance of rust with the aluminized mirror? Again, Im new to telescopes and have very little knowledge. The scope is a used Orion XT10.

I'll let others here comment on the effects of actually rubbing though the coatings down to the actual glass (personally I doubt you did this!) 

 

As far as the film on the mirror I have a few thoughts:

You used to much soap. Or you used colored-scented soap. In a quart bottle all it takes is a single drop of clear, unscented soap in your mix to get the job done. If you didn't...

 

Then there was something on the mirror which dissolved and spread into a film. I had this happen on my 8" mirror from the foam strips under the mirror clips. They left a residue on the mirror which made a film. Took forever to get rid of the film. What finally worked was to rinse the mirror in straight 91% rubbing alcohol and then clean again with distilled water, a drop of soap and no alcohol. 



#3 Miksubi

Miksubi

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 09 Dec 2023

Posted 10 December 2023 - 03:26 AM

Thank you for your response. I used the blue dawn dish soap so it was a colored scented soap, I took some photos of how it was after the initial cleaning, and from the top of the scope as it is now. https://imgur.com/a/PGNFgxs any help is appreciated!
  • RoofMonkey911 likes this

#4 Tony Flanders

Tony Flanders

    ISS

  • *****
  • Posts: 23,523
  • Joined: 18 May 2006
  • Loc: New Lebanon, NY and Cambridge, MA, USA

Posted 10 December 2023 - 06:14 AM

Might be a dumb question, but how would I know if I've rubbed off the coating on my primary mirror?


I doubt you could rub the coating off the mirror even if you tried.

A friend of mine with a very old mirror once went to a local expert in Boston to get his mirror recoated, and I figured I would take mine along too, because it was looking mighty gunky and spotted. The mirror recoater took a look at my mirror, flicked all the dust off, and polished it with a clean piece of fabric. Put a lot of elbow into it too; I would never have dared push that hard. When he was done the mirror looked (and worked) as good as new.



#5 astrokeith

astrokeith

    Vanguard

  • *****
  • Posts: 2,234
  • Joined: 14 Mar 2010
  • Loc: Surrey, UK

Posted 10 December 2023 - 06:31 AM

As suggested pretty sure your initial cleaning left a film of something oily over the surface. It was very dirty and I would expect to do 2 or 3 washes.

 

The coatings are quite hard, but what they cant stand is grit like dirt. Anything sharp will penetrate the every thin coating. If you had rubbed hard enough to remove the coating, you would have removed at least some of the aluminizing, which from the photo you havent.

 

Looks good to me!



#6 RoofMonkey911

RoofMonkey911

    Viking 1

  • *****
  • Posts: 955
  • Joined: 22 Jun 2022
  • Loc: Palmetto, Florida

Posted 10 December 2023 - 07:13 AM

Thank you for your response. I used the blue dawn dish soap so it was a colored scented soap, I took some photos of how it was after the initial cleaning, and from the top of the scope as it is now. https://imgur.com/a/PGNFgxs any help is appreciated!

From the images you provided, that mirror looks 1000% better!



#7 Messierthanwhat

Messierthanwhat

    Messenger

  • -----
  • Posts: 442
  • Joined: 08 Dec 2013

Posted 10 December 2023 - 08:32 AM

I think you did a phenomenal job on that mirror. I'm pretty sure I wouldn't even have thought it was salvageable.



#8 sevenofnine

sevenofnine

    Fly Me to the Moon

  • *****
  • Posts: 6,602
  • Joined: 16 Apr 2016
  • Loc: Santa Rosa, California

Posted 10 December 2023 - 11:38 AM

Only from what I've "read" so experts may correct this but as I understand it there are two coatings on the surface of the glass. The usually aluminum reflective surface and then a top coat of clear So2 to protect it. This final surface is pretty tough but it can be scratched/sleeked by rubbing actual dirt that lays on the surface. That's why you rinse the mirror first then clean fingertips with soapy water to wash the top coat. As far as your rusting concerns, aluminum doesn't rust but the screws holding the clips might and spread to the top coat. They should be replaced with new ones. Your cleaning looks good! waytogo.gif


Edited by sevenofnine, 10 December 2023 - 11:39 AM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics