Mirror cleaning procedure

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Mirror cleaning procedure

Postby edward-fraini » Mon May 25, 2015 6:16 pm

There was an interesting string of emails on Netslyder about mirror cleaning. I would like to hear from the Forum followers on this as well.
I personally have had the misfortune of getting acetone on the "inked" center spot on my DOB as they mentioned and it was an instant disaster. I also have had discoloration of the mirror with denatured alcohol. What I have read is that the quality of the mirror coating has a lot to with this. There are many chemistry reactions for both alcohols and aldehydes that are catalyzed by both silver and silicon dioxides. If you are buying solvents from the Box Store I would say Buyer beware. I worked in a plant that made acetone as a byproduct, which we purified to reagent grade. It was not unusual to find aromatics that can lead to bluing of the mirror in store bought solvents, both acetone and alcohols. I tested store bought paint grade acetone in our lab it is was full of other additives and impurities.

Not saying you should not use solvents as mostly likely you will be fine. Saying you may have some uncontrollable factors you are not aware of.

Here is the bigger point I believe. When you think your mirror needs to be cleaned, mark it on the calendar and wait year. Sure the math says there is an effect but can you really tell it at the eyepiece.

After struggling with this question for years I find myself in the Wick It camp. I periodically flush with distilled water just to remove dust and wick up droplets. Never get 100 percent of them cleaned up. Cleaning as in cotton ball and solvent flushing is something I have not done to my current DOB in four years. I really don't think a couple of dust rings on the mirror make much difference. Think about the surface area equation. The covered surface of a dust ring is pretty small compared to the total and the effect is not very relevant when compared to say collimation. I start the evening with the DOB collimating and re check it every couple hours as the mirror continues to settle in.

Let me throw in another observation. I used to follow the advice about adding a drop or two of Dawn to the water. For me that turned out to be a bad thing as well. My old 16 inch DOB got regular cleanings, why too often and why to aggressive. I found over time a film of soup residue built up on the mirror and I had no choice but to have it re coated.

Would really like to hear what the guys with big DOB's do with their cleaning routines, both time interval and procedure.

Ed F
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Re: Mirror cleaning procedure

Postby steve-fung » Tue May 26, 2015 11:32 pm

Ed, thank you for sharing your valuable experience and insightful comments. I am in the process of getting a "big" Dob, so now I know what not to do. This also reminds me of Uncle Rod's (Rod Mollise) blog on "Mirror Cleaning Madness"

http://uncle-rods.blogspot.com/2012/12/mirror-cleaning-madness.html

Here are a few other websites describing how to clean optical surfaces:

http://www.astro-tom.com/tips_and_advice/cleaning_optics.htm
http://www.astro-physics.com/products/accessories/cleaningproducts/optcs-instructions.pdf
http://www.company7.com/library/clean.html

Even though these are from reputable sites, I too disagree with the use of organic solvents such as alcohol and acetone because of potential damage to optical coatings. As for myself, I use distilled water after blowing off loose debris, and if that does not work, I use very dilute solution of mild liquid detergent followed by distilled water rinse again. Interesting that you mention despite careful rinse, you still find accumulation of detergent residue built up over time. Maybe I need to rethink about the use of detergent as well.
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Re: Mirror cleaning procedure

Postby edward-fraini » Wed May 27, 2015 10:30 pm

I very much enjoyed Uncle Rods, web page. Not just the comments on mirror cleaning but other random topics as well, thanks for posting an interesting link.

Ed
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Re: Mirror cleaning procedure

Postby edward-fraini » Wed May 27, 2015 10:39 pm

Another thought comes to mind.

A while back there was a guy at an El Dorado Star Party that was doing something that look promising but it seems to not have gone anywhere. He was dissolving polystyrene (I think but it might have been Polyethlene) in a volatile solvent. It was all secret ingredients. He would use a pump spray bottle to spray the solution on your mirror. While the solvent was drying he collected your money. Once the solvent had evaporated a film of polymer was left that he peeled off and it took with it every bit of foreign matter and the mirror was like new. Looked very promising to me at the time. No idea why it didn't catch on but there must have been a fly in the ointment somewhere.

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Re: Mirror cleaning procedure

Postby henryv1598 » Thu May 28, 2015 8:20 pm

edward-fraini wrote:Once the solvent had evaporated a film of polymer was left that he peeled off and it took with it every bit of foreign matter and the mirror was like new. Looked very promising to me at the time. No idea why it didn't catch on but there must have been a fly in the ointment somewhere.


My guess is that people with poorly coated mirrors probably were seeing loose coatings come off with the film. I'm sure it was designed not to stick to the mirror coating, but I bet here and there it did and he ended up taking off coating in several places on some mirrors. It's just a guess, but I wouldn't be surprised.

Neat idea though.
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Re: Mirror cleaning procedure

Postby buster-wilson » Fri May 29, 2015 2:58 pm

A cleaning kit as you describe is/was for sale on the market. When we were at NEAF I watched a demo of it being put on and after a time it was peeled off much like Saran wrap would do. I didn't see the mirror up close before but a after look didn't look great to me. Don't remember the name of the stuff. Search for a Gun Cotton procedure that has been used for years before. Unless there is a special need for something to be removed off a mirror the usual methods are the best place to start. Have known of a local mirror that had some sort of plastic stuff sprayed on that was extremely hard to remove. As for the "soap" to be used in the water I once used some of my left over hard contact lens cleaning solution. Worked normal or less than. Don't know if it is still on the market or not but Amway had a very good product called L.O.C., liquid organic cleaner that worked very well and some have used dog shampoo. Sometimes its best to not reinvent the wheel. *BW*
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