Resilvering in the South West

[GBHgpJON]

Just wondering if there is anywhere/anyone in the SW that undertakes mirror resilvering? Always fancied building a Dob, using an 8inch mirror that came into my possession a good few yrs ago!.....Trouble is over the years in storage the silvering has suffered........

 

 

[ronin]

Not aware of any. Galvoptics in Essex used to resilver, but their web site has altered and what they do now is a bit undefined.

Recall reading one in North London, but they have dropped off the radar also. Then it could come down to asking Orion Optics or Oldham Optics - likely Oldham is the best option. However all are a way from Devon.

You could contact Exeter Uni. Think they have a bit of an Astro section so maybe they may know someone. Owing to centers of population I would have guess that the nearest if there is one would be Bristol area.

Think this is the N London one:http://www.scientificmirrors.co.uk/Services.html

Head to google and search for: "telescope mirror recoating uk" As you enter the text it is one option tht google presents for selection. Several options for companies appear. I am not going to search each one.

[John]

I know someone who makes mirrors and is based in the South West but he uses Galvoptics for aluminising and coating them I believe.

[GBHgpJON]

Thanks for the answers, one of the reasons I'd asked was because the firm's that came up on good ol' Google were a distance away, and wondered if anyone did it on a small scale Devon style.... I suppose cheaper easier available prebuilt dobs make it less viable these days. 

[ronin]

Doubt it is the prebuilt aspect more likely just a low demand for such. There are not that many people that use a scope, many will have refractors or SCT's and the remaing reflectors will need a resilvering at about 8-10 year intervals, and it is not a viable thing to do for a small mirror. Would think that resilvering a 6" mirror would cost the similar to a new mirror or new scope.

Whoever oes it needs to strip back the existing material, likely very lightly surface grind the mirror, then realuminise and add the protective coating.

A 6" f/5 or f/6 mirror from TS is €181, about £150.

[Stu]

It is quite easy to pack a mirror and ship it to any of the companies mentioned. I sent a 12" and 10" to Orion Optics and received them back safely, and very nicely coated.

[SilverAstro]

4 hours ago, GBHgpJON said:

 fancied building a Dob, using an 8inch mirror that came into my possession a good few yrs ago!.....Trouble is over the years in storage the silvering has suffered........

If you know that the figure of the mirror is especially good then it would be worth sending it to be re-coated (re-aluminized), as others have said, otherwise the cost of a new dob (at 8") from the far east makes them contenders.

If you want to make it a true diy / nostalgia project then you could do as we did when the dinosaurs were young - re-silver it at home ! ( I did know a chap in mid Dorset who built his own aluminizing vacuum chamber but that is another story and he is long gone ). Silver Nitrate (still available on Ebay !! surprise ! ) and a reducing agent etc is needed. It is messy, and the usual warnings apply, the pro is that the reflectivity of a new silver coating is better than aluminized, the con is that it is delicate and not long lived.

HNY

PS Edit , oh I forgot, - removing the old aluminium coat would have been easy using caustic soda once upon a time, but I am not sure about the modern (silicon dioxide?) overcoatings ??? advice needed

 

[Astrobits]

The only commercial options that I am aware of are as listed in previous posts above.

If you want to remove the coatings yourself you can but if sending to any of the above commercial outfits then let them remove the old coatings.

Caustic Soda dissolves glass.   Yes, it will attack your nice mirror surface as well.  You don't need to remove the overcoat before removing the Aluminium, treatments below also remove the overcoat.

You can use Hydrochloric acid ( diluted ) if you can get it but beware nasty fumes and getting some on your skin. Or use what I would, Ferric Chloride. No nasty fumes and much kinder to your fingers if you get it on them. Just takes a bit longer.

As for Silvering yourself this is potentially dangerous as the formulations not only produce a nice silver coat they also can produce Silver Nitride -- which is explosive. Care must be taken to follow all safety procedures.

Aluminising yourself is also possible with some fairly expensive equipment.

Nigel

[Mognet]

Galvoptics still do resilvering work. Looks like it's £85 or £99 for your mirror depending on coating thickness http://www.galvoptics.co.uk/optical-components/telescope-products-andamp-services/telescope-mirror-coating---primary/

As it's a project dob, then another alternative is to keep an eye on Astroboot for mirrors. I think the 8" are usually sold for about £50 when they come up. They currently have a couple of 130mm (5 inch) mirrors and mirror sets in A1/A2 condition

[GBHgpJON]

This is my dilema, pay for recoating/ shipping to and fro.........or buy secondhand cheaper. Perhaps I could get it checked out for wave etc first? 

It was hand ground by a local mirror guru who I believe is no longer alive, and also believe it is of good quality, but it would be good to know for sure before throwing time and money at it. Have contacted local AS to see if they can throw any light at it.....so to speak!

Thanks once again for your replies...........

[Stu]

21 minutes ago, GBHgpJON said:

This is my dilema, pay for recoating/ shipping to and fro.........or buy secondhand cheaper. Perhaps I could get it checked out for wave etc first? 

It was hand ground by a local mirror guru who I believe is no longer alive, and also believe it is of good quality, but it would be good to know for sure before throwing time and money at it. Have contacted local AS to see if they can throw any light at it.....so to speak!

Thanks once again for your replies...........

Perhaps an experienced eye could have a check over it visually by star testing etc to get a feel for how good it is. My, perhaps incorrect, feeling (based upon nothing other than a hunch) is that even modern hand ground mirrors are perhaps likely to be better due to better availability of testing equipment to refine the figure etc.

[Stu]

3 hours ago, Astrobits said:

Aluminising yourself is also possible with some fairly expensive equipment.

I'm not sure I fancy Aluminising myself Nigel. Alhough somewhat rounded and of large aperture, I suspect I am far from the correct shape to be optically useful, more spherical than parabolic certainly  

[Astrobits]

Glitterball perhaps?

Nigel

[Stu]

12 minutes ago, Astrobits said:

Glitterball perhaps?

Nigel

Tee hee . That's a scary image though  

[timwetherell]

When I used to work in a lab long long ago, we had an aluminium evaporation system for creating metal contacts on semiconductors. It's relatively simple, just a vacuum chamber, a rotary vacuum pump and an electrical heater to melt the aluminium. I did play about with silvering optics in it just because I'm that kind of guy  and I have to say the results were far from brilliant! It's very hard to achieve an even coating with good uniform reflectivity in a small chamber of the type one could hope to have at home. The better way to do this is with a large turbopumped electron beam deposition system. We had one at the uni I worked for in Australia - the size of a mini and the cost of a Lamborghini! So probably not something for one's garage.

[Astrobits]

I have come across a spray-on method of silvering mirrors. Cloudy Nights forum has some info with regard to the application on astro mirrors:

http://www.cloudynights.com/topic/438374-silver-spray-on-instead-of-alumnimizing/

Kits are available from:

http://angelgilding.com/

and:

http://www.peacocklabs.com/products.htm#silveringsol

Should be interesting to try this sometime.

Nigel