Time to clean Mirror?

[V8cressida]

G'day. Getting back into the hobby again..... I have a 10" dob...Resides in my gararge in plastic. Decided to have a look inside and this is what I see !

http://i82.photobucket.com/albums/j245/v8cressida/P1010119.jpg

Clean time ? What should I use?

This scope has a mirror fan which I must admit I tend not to use much. Could this be a dew problem? As quite often particularly in winter the outside case is wet when I pack her away.

Cheers . V8

[Starkler]

As a general rule, you shouldn't seal up any optics that are damp, including caps on eyepieces etc.

As for the mirror, there are countless threads on this site re cleaning mirrors already and the search function will see you right.

i would start with a rinse under a lukewarm tap to wash away any loose or water soluble crud before a soak in a lukewarm bath with a tiny bit of dishwashing detergent, followed by another rinse of running water, followed by a final rinse of distilled water.

[jjjnettie]

That looks pretty well stuck on too.
You don't want to have to rub hard to get it all off.
That lukewarm bath that Geoff recomended should be for at least a quarter of an hour.
Rinse off the muck and repeat the soaking if needed.
Once clean, I mop up the drippy water on the mirror with a slightly damp, antistatic cloth, that is only used on this mirror, then finish with a hair dryer so it dries quickly and evenly with less chance of getting dried water marks/spots. Which as we all know is one of the most frustrating things about washing these darn things.
But everyone has their own ideas on how to treat their beloved mirrors.
Here's how they clean the huge 8 metre mirror at the Gemini North Observatory.
"Through experimentation with various detergents, technicians have found that the most efficient way to clean it is to mop the mirror surface using natural sponges soaked in a detergent popularly marketed as horse shampoo, which they purchase at a general store in Hilo, Hawai'i. Optics Technician Clayton Ah Hee, who supervised the actual washing, said the soap is used because it is a strong detergent, yet is not abrasive to the multi-million dollar mirror's delicate surface, and leaves no residue. "We've found the combination of the natural sponges and horse soap to be the most efficient way to get the mirror surface completely clean," said Ah Hee. "I know this sounds kind of simple, but sometimes the simplest solutions are best, even with something as leading-edge as the Gemini telescopes. And the horse soap really works.""
Here's the link.
http://www.gemini.edu/index.php?option=content&task=view&id=60

[xstream]

You could try using this How To (http://www.iceinspace.com.au/index.php?id=63,345,0,0,1,0)from our Projects & Articles section.

[Zuts]

If it's that good maybe we should all be using horse soap; and I dont mean just on our mirrors :lol:

Paul

[V8cressida]

Using the knowledge I have gained from you lot, I washed my 10" mirror today.

Unfortunately it doesn't have a happy ending!

I used the washing up liquid/warm water soak for 15 minutes, cotton ball method.
The thing is, while I didn't drop the mirror or anything, The blemishes (see original pic) will not come off! And yes I did try in exasperation rubbing a bit harder than I should of (didn't hurt the surface though).

Looking closely it makes me wonder whether this is more of a corrosion thingy. We live close to the beach (salt air ?).

So my mirror really doesn't look much better than before. Possibly all caused by poor use/storage procedures. We do get a lot of due/frost depending on the season.

My scope is always kept in my colourbond gararge so I would have thought it may have less of a temperature difference than one kept in the house......I haven't been using the mirror fan. And quite often my viewing times are on a whim and the scope quickly gets set up and covers are off and i'm into it.
I have noticed the outside of the case gets wet to the touch some nights!

When I'm finished the big cap goes back on and the scope is stored in an UPRIGHT (mirror at lowest point facing up) position. Now in hindsight that is probably a daft thing to do because if the mirror is wet, storing it face up is bound to have particles (if it isn't a corrosive thing) drop and stick to it!
Opinions ?

V8

[Kokatha man]

Hi V8 - I saw your original post and thought plenty of others would respond with better cleaning tips than me - but to be honest I did think that it looked like corrosion....the white deposits etc. In the old days that usually meant having the alum. coating stripped and recoated, but if it has a "top-coat" maybe there's other options nowadays.....

Regards, Darryl.

[stephend]

If you keep the lens cap on, particles can't fall on the mirror during storage, I would think. Maybe you left it off once or twice?
The fan is to equalise temperature across the mirror to prevent distortion, I don't think it can reduce condensation.
It almost looks as if there has been a chemical reaction between the mirror surface and the particles.
Interesting thread .... hope you get a solution.

[V8cressida]

Never Left the lens or eyepice caps off. I will buy a collimator line her up and see what happens. Worst case senario = new mirror. I noticed that Andrews communication sells them for $389.00

V8

[Kokatha man]

Hi again - I know I'm getting long in the tooth and have been out of the game for a long time - but surely the mirror can be re-aluminised? $400 is an expensive way to go?

What's the story out there re re-aluminising?

Regards, Darryl.

[Night Owl]

I put up a post before I read the others, and it looks like I was right. Salt corrosion of the raw alluminised mirror.

If you are smart you learn from other peoples mistakes.

I think my new rule # One is do not take your scope near the coast! Unless you are going to wash it after each session.

Too bad mate, looks like a re-silvering job.

[erick]

Interested to hear what the view is like with that level and form of abnormality on the mirror. Perhaps > 50% of normal mirror surface is left. If the light striking the spots is not reflected back to the secondary, but absorbed or scattered, I'm guessing it will be dull, but not completely hopeless?

[xelasnave]

I have had the experience with a mirror I thought I would get rid of the small scratches:whistle:.. I was real new then;)...so I polished the thing with some stuff and was surprised to find most of the mirror gone:eyepop:... you could still use it but the along came a new scope so I never got it resilvered. but it surprised me how well it worked really.
alex:):):)

[Kokatha man]

Hi all - this thread, and mine and other posters, makes V8's dilemma (possibly in the future) my own!

I live 600-700 metres from the beach here, and salt spray does develope on the car windscreens. Which means care and protection of my mirror is essential.

Who does re-aluminise mirrors? In the "old-days" there were plenty of firms that would re-silver them (you only had to impress on them that it was the front surface that you required the silver deposited on) but for aluminising we here in Adelaide had to freight our mirrors to Sydney. In fact, one could silver a mirror oneself if you were game, but it was both an art and skill to successfully do such.

So who does re-aluminising now in Aust?

Regards, Darryl.

[MrB]

Francis Lord Optics used to do it years ago, but there's no mention of it on their website now, ask 'em anyway: Francis Lord Optics (http://www.flo.com.au/Optical_Manufacturing.htm)

Got all the gear here to make my own chamber, might get around to it one day!

[stephend]

I have seen various articles on silvering mirrors; this one is typical ...

http://www.textfiles.com/science/silver.txt

sounds like great fun and you probably end up with a superior surface, but I doubt that it's possible to buy nitric acid in Australia.

[fringe_dweller]

there is a place that does aluminising in adelaide Darryl, a mate used to make newt/dobs for a sideline living here, before the cheap chinese stuff killed it off, Ill find out the name, it is a prominent company. hmmmm was it an arm of AWA? only thing is you need to do a batch of aluminising, , as it is lot cheaper than getting one done, they throw it in with a batch of other customers - we have at least 3 mirrors between us we want re-aluminised, keep putting it off! only thing is, it isnt the hard outer coated type, which they do in sydney i think.
I think it works out to less than a 100 bucks each, the more you have the cheaper it is, to a point.

[xstream]

For coating the man you need to contact is Isaac, he handles up to 24"
Chi Qin Co.
Fax (02) 95917588
Mobile 0412957809

[rmcpb]

Before you get into the realuminumising bit, give the mirror a few runs under the stars as see if it is still usable. If so you could put off the resurfacing for a bit longer.

[V8cressida]

ok. So if the mirror HAS had it, and I either get it re surfaced or replaced, how can I stop this from happening again?! Are there any scopes that are less suseptable to this prob?

V8

[madtuna]

I'm no expert but to save it happening again you just may need to inspect and clean more often due to your proximity to the salt, and never seal it while the mirror is dew affected.
I'd also imagine the same thing could happen to a premium grade mirror.

[wasyoungonce]

AWADI (Adelaide) does optics for the military and government. I did a Laser course there and had a tour of the optics branch manufacturing branch....very impressive, they do coatings. Don't know if they do private stuff though and it would probably cost a pretty penny.

[fringe_dweller]

my friend definately had quite a number of mirrors coated there - whoops, maybe i'm giving out trade secrets :scared: that was probably nearly 8-10 years ago he last had them do it
maybe he had a mate in there? lol i dont remember him saying that tho.
he doesnt do it anymore so i'm not compromising him, i have 2 mirrors which were coated there, was pretty good, its usage out in the field that sped up the process, getting dewed up ect.

anyone thinking of sending away their mirrors should add an identifying scratch to unused side of mirror, as he once had a 6 inch mirror come back from interstate, and it was a different one to one he sent! it was only the identifying scratch that saved the situation! after some argueing i believe, and the swapped one was of very bad quality, he wasnt happy!