How to Clean a Mirror?

Miaplacidus (Brian) · #1 26-01-2006, 11:32 AM

Calling or newtonian owners,

I've been searching the forums and How-to's, but I can't find a thread or an article that tells me the best way to clean a primary and secondary mirror. Can someone please help by providing details and tips about how they cleaned theirs, and what to avoid in the process, or maybe point me at some suitable web site?

Thanks,

Brian.

davidpretorius · #2 26-01-2006, 11:38 AM

Brian, the is a post by bird in here somewhere.

basically, warm water, with some detergent, leave mirror under the water for 20 minutes then slosh the water over the top of the mirror whilst leaving the mirror underwater. Any determined stains, use a cotton bud to dab them.

Rinse under demineralised water and then stand on its side. The heat from the water and soaking for 20 mins should help it dry.

Thats it.

I have done mine twice and have had no probs!!

barees63 · #3 26-01-2006, 12:10 PM

Check this out http://www.wwnorton.com/astro21/sandt/optics.html

I cleaned the kitchen sink really well then ran the mirror under the tap for a bit then added a couple of drops of dishwashing liquid to distilled water and poured this onto the mirror, then dragged (under its own weight) a piece of sterile cotton in a circular motion from the center out, I repeated this once (my mirror had quite a film on it) then I sat the mirror on edge on a folded teatowel (still in the sink) and rinsed thoroughly with distilled water, at this point there were just a few drops sitting on the mirror surface so I carefully wicked them off with the corner of a tissue.. after this my mirror looked really bright, by the time I got it back in the scope it had dust on it again

Miaplacidus (Brian) · #4 26-01-2006, 12:18 PM

Thanks guys, I knew I wouldn't have to wait long before someone came along with the answer. (David, you're always on here. Don't you have a day job?) I appreciate the handy article, Bruce. I'll study it up before I attempt anything.
I haven't been in a hurry (the luxury of multiple scopes I guess), and I know all the advice about never cleaning optics unless they REALLY need it, but once I disassembled both newtonians, I couldn't believe the amount of crud I had on the old dob. Since then I've persuaded myself that I just can't see as much as I could before.

Cheers,

Brian.

PS Where do I get demineralised water?

Satchmo · #5 26-01-2006, 02:57 PM

Quote:

Originally Posted by Miaplacidus

PS Where do I get demineralised water?

Brian

Demineralised is basically distilled water , which you can buy from the local garage.

I wash my 14" mirror about every 6 weeks as I live in a bush region and get a greasy film of Eucaliptus oil on my mirror ( so I start my swabs with methylated spirits before detergent). This film is very tenacoius ( sp) and any residue can easily be seen by breathing onto parts of the mirror and looking at the condensation pattern. When the mirror is free of grease the breath pattern will be smooth and uniform. Aluminisers use this breath test also to see if the mirror is clean enough for coating ( trade secret there !)

Sydney water is fairly soft so I've never bothered with distilled water. I use warm tap water for the final rinse and dap of remaining drops with cotton wool while blowing . Any final lint can be blown off with a camel hair brush. Works for me...

Mark

cjmarsh81 · #6 26-01-2006, 04:26 PM

You can get demineralised water from Woolworths for about $1.50 I just got some and cleaned my secondary mirror. Or as Lambda20 just stated distilled water will do the same job.

Dobman (Simon) · #7 26-01-2006, 06:21 PM

I,m sure there was an article on cleaning mirrors in either Sky & Space or Aust Sky & Telescope. I think it was fairly recently but I cant say for sure . I'll go thru my back copies & let you know if i find anything. Otherwise, you could try going to the magazine web sites and searching

Good luck

norm · #8 26-01-2006, 07:46 PM

Hi,

On the subject of cleaning mirrors. A word of caution. I read it on the net where someone was cleaning their primary under a kitchen sink. When he lifted the mirror after cleaning it, he forgot about moving the tap/mixer away....you only need to imagine what happened to the mirror!

Just something to keep at the back of your mind.

Roger Davis · #9 27-01-2006, 08:17 AM

Also remember to clean out the sink before your start!
Grease from Australia Day lamp chops or that bit of tomato or bbq sauce doesn't help the mirror surface.

BC · #10 14-03-2009, 12:34 PM

Hi,

I know this is an old thread, but methylated spirits is mentioned. I've just had my first go at cleaning the mirror and while the dust has gone, the surface is still filthy. I live in the bush so maybe the eucalyptus oil has caused this. I tried wiping with metho and re-washing, but it hasn't helped much. Would you soak the surface in metho or would this potentially damage it?

Thanks,
Bruce

Quark (Trevor) · #11 14-03-2009, 07:46 PM

Hi Guys,
There is an excellent step by step, illustrated article on how to wash a Newtonian mirror, written by Mike Salway (iceman) at the following link, on the IIS Articles section.

http://www.iceinspace.com.au/63-345-0-0-1-0.html

Regards
Trevor

erick (Eric) · #12 14-03-2009, 10:15 PM

Quote:

Originally Posted by BC

Hi,

I know this is an old thread, but methylated spirits is mentioned. I've just had my first go at cleaning the mirror and while the dust has gone, the surface is still filthy. I live in the bush so maybe the eucalyptus oil has caused this. I tried wiping with metho and re-washing, but it hasn't helped much. Would you soak the surface in metho or would this potentially damage it?

Thanks,
Bruce

Might sound silly, but have you tried a little clean eucalyptus oil on a small spot (try the very centre - inside the secondary shadow) to see if that lifts what you suspect to eucalyptus gunk. And after rinsing how does the surface look - any obvious damage? If it seems to work, maybe carefully lift the gunk with gently dabbed euc oil, then wash as per normal - a little detergent to lift residual euc oil and the rest.

BC · #13 15-03-2009, 10:20 AM

Thanks Quark, I should have said up front that I used the iceman article as the method of choice.

erick, eucalyptus oil may be a bit radical; or maybe do a good job. I will ponder that one before pursuing it.

For now it's reassembled. I would mention that I made a template to check the centre spot put there by the vendor. It would be 1-2mm out, so I have marked it up and recollimated and will check out the results when things clear up.

Bruce