Mirror resurface / re-silver

[vespine]

Short version. Does anyone know of a professional mirror resurface service in Melbourne?

I've found a couple of very old threads here but nothing helpful, one shop which is no longer in business. Looks like bintel don't even have a shop in Melb anymore, obviously I haven't spent enough on astronomy in the last 10 years :)


I have a 12" Lightbridge I bought when they 1st came out, must be over 10 years ago now. I have looked after it, always has the dust cover on whenever it was not in use and I never touched the mirror with anything. Haven't used it for a while so I thought I'd give it a once over and I'm quite shocked how bad the mirror looks. It's covered with tiny black spots when I've inspected them under a magnifying glass, it appears like the silver is corroded off. My guess is just years of moisture, maybe some "spores", mildew, who knows...

After some further research, it appears 10 years is actually not a bad life for a primary mirror, so I'd be happy to part with a few hundred dollars to get it spick and span.

[billdan]

Hi,

Its unlikely you have a sliver coating on your mirror, as silver tarnishes very quickly and 6 to 12 months performance is all you get. Your mirror will have an aluminium coating which indeed does last for 10 years.

The only place I know of to get it re-coated is Saintech which is north of Newcastle in NSW.

www.saintech.com

Cheers
Bill

[vespine]

Thanks for that, yeah i think I knew it was "actually" aluminium, but "re-aluminium" has a terrible ring to it :)

The 12" inch mirror weighs quite a lot, would be great if I didn't have to ship it, but thanks for the info anyway, might have to take it if I have no other choice.

[AstroStudentUSQ]

"Telescopes and Astronomy" based in Adelaide also does mirror re-surfacing, with lots of people posting their mirrors there to be re-done apparently.

http://www.telescopes-astronomy.com.au/telescope-mirrors-blanks-tools-glass-aluminising.htm

The owner (Matthew) is looking at selling his aluminising machine but I believe he still has it currently.

[vespine]

That's a little more than I was expecting, I thought it would be closer to $200-$300. $400 plus the shipping that's practically half the price of a new scope..... resurface a mirror every 10 years or buy a new scope every 20... Decisions decisions.

Anyone recently done this? Might try to give it a proper clean with distilled water and cotton balls and see how bad it really is..

[torana68]

I wouldn't re-coat a GSO (for example) mirror , Id buy a new one, I would re-coat a tested hand made mirror, maybe have yours tested in Adelaide? if its average just buy a new one.

[billdan]

Try cleaning it first, soak it in water with some dish washing liquid for about 20 minutes. Then use the your finger tips to clean it (keep your finger nails away from it). Then rinse with distilled water.

Under water your finger tips will not do it any harm.

[vespine]

That sounds pretty good. This might be a stupid question, but would you un-mount it from the cell first? or just soak the whole thing, just make sure it's all nice and dry at the end...

i have removed the mirror and cell from the scope, I'm thinking I'd probably prefer to leave it mounted on the cell, unless someone has a reason why that's a terrible idea.

[vespine]

https://i.imgur.com/o3MJsZq.jpg

this givers you an idea of what it looks like..

On one hand, it's probably less than 1% of the mirror, am i being overly precious? or is this stuffed ?

To be honest I haven't really noticed anything that bad when I've used it, but is it like when your breaks go soft over time but you don't notice, until they get fixed :)

[doppler]

Hold the mirror up to a light and look from behind, if there are bits of coating missing you will see the light through them. The coating is thin so some light may show but any bad blemishes will really stand out. Looks like dust to me on your pic though. A bit of water won't hurt the cell and the colimation won't go out by much if you leave the mirror in the cell.

[AstroStudentUSQ]

A new 12" F/5 primary from Bintel, 1/14th wave, 91pc reflectivity, is listed at $679...

12" Resurfacing with Telescopes & Astronomy to the same reflectivity as Bintel is listed on their site as $405, but that is an old price listing... And I imagine fragile postage would be quite significant. I don't think you would be getting much change from $500 with that route...

I don't see any other choices other than either get that mirror re-surfaced, or get a new mirror, or buy a new telescope... or just embrace the current imperfection

[billdan]

Looks like dirt to me as well, so a good clean should be OK.
I leave mine in the cell when cleaning it and I use an air compressor with a hankie over the nozzle (so I don't blow more dirt onto it) and blow dry it. Stops the water from settling and beading.

[vespine]

I thought it was dirt at first too until i examined it under a loupe too, and the light test looks pretty terrible:

https://imgur.com/a/P03p8

Thanks for all the tips, great help, now I can make a well informed decision.
Cheers.

[vespine]

Have to say, kinda looks like the stars burned into the mirror :)

[fsphotography]

Longman Optical.
Tasmania. Ph. 03 627 21785.
Had a 300mm mirror done a couple of years ago,its the maximum
size they can do, then just over $300+post. Good job and quick turn around.

[croweater]

Hi Frank, Was that for aluminium with SiO2 overcoat? Cheers, Richard

[fsphotography]

Hi Richard,
Yes that was for aluminium and coating. I don't recall which coating.
Frank.

[croweater]

Thanks Frank :)

[doppler]

I guess that's what happens when you don't clean a mirror often enough, bit like leaving a bit of bird poo on your car, after a while it eats into the paint. Give it a good clean, a few (even a lot) of pin prick holes will have little noticeable effect on your viewing.

edit: I just had a look at a couple of my old project mirrors and yours dosn't look that bad in comparison.

[StuTodd]

Wow you people love spending money. There are hundreds of DIY walk throughs on t'internet regarding the cleaning and self silvering of telescope mirrors..

I've done a couple in the past, just take your time and get the mirror clean first.