Local mirror silvering services ?

I've been googling and reading about telescopes for the last week or so ever since I bought a little Aldi National Geographic telescope that clearly showed the craters on the moon. Amazing.

I thought a 6" or 8" telescope would cost a fortune so started reading about diy telescopes and this led to mirror grinding - seems interesting, and I usually see a line that goes something like this .........................

".............. after you have ground the mirror its quite cheap to get it silvered by your local mirror silvering place ..................."

Maybe I'm not googling the right terms , I get sites that look to be specialising in expensive custom optical jobs for industrial applications and scientific laboratories.

Has the local cheap corner shop mirror silvering place disappeared just like the local foundry has ?

Once all diy costs are considered, especially silvering + protective coat, is it cheaper and quicker - but far less interesting - to buy mirrors ?

Bill

If anyone is interested page 51 of this book

**LINK**

And then googling Brashears Process opens the door to other websites

Bill

I used to send mine off to be aluminised and overcoated. Can't remember where now but I presume such firms still exist?

I did silver a 12" mirror myself once which wasn't particularly difficult. The problem nowadays would be getting hold of the chemicals - IIRC silver nitrate, concentrated nitric acid (for cleaning the glass), ammonia, sodium hydroxide, and dextrose. I got my chemicals from the local chemist but those days have long gone unfortunately.

Silvering can be a bit nerve racking as you can get silver fulminate formed during the process if you don't mix the chemicals properly!

John

Hi Bill

I have used this company in the past.

**LINK**

I produced a 12" mirror some years back now by the "walking round the oil drum process"It took ages but was strangely interesting for so slow a process. The thing that fascinated me was the ability to create a surface to sub light wavelengths essentially by using varying grades of 'mud' and your own hands. It's not difficult but it does need care. I think galvoptics do pyrex blanks and grinding and polishing compounds too.

regards Martin

Thanks for the replies. Its encouraging to "meet" 2 people who have done 12" mirrors.

I found this mob in Australia who seem to be the equivalent of the link in Martyn's post above. They will send a pricelist if you email them.

I also found this diy site http://www.webstertelescopes.com/silvering.htm

and being as it seems to be a backup of a site that is down, I have shamelessly copied what he has written and pasted it into a word document in case it gets lost, it seemed to be good clear instructions. Can email it if anyone ever stumbles across this post in future.

Bill

+ VAT, so about £80Orion will do a 6" mirror for £64

But it depends what you call a fortune...

www.firstlightoptics.com/reflectors/skywatcher-explorer-150p-ds-eq3-2-eq3-pro-goto.html

Even cheaper with an Alt-Az mount.

Neil

Thanks Neil,

Am starting to question viability of building a 6" or 8" from scratch - after allowing for some mistakes and time spent and costs of individual parts, unless I get lucky on ebay auctions, could end up costing same as a cheap one.

Couldnt see the £64 mirror on the Orion site, cheapest I could find was £120 - am I looking in wrong place ?

8" $649 here

Bill

www.orionoptics.co.uk/OPTICS/mirrorrecoating.html

Table at the bottom, 130-180mm £64 +VAT +shipping, + you have to send them the blank, so getting pricey...

I think you were looking at the cost of a complete mirror.

My thought is that making a small mirror is probably viable for either very small (4" where you don't need to parabolise it and very little glass to remove, or if you want to get the technique before tackling a larger mirror (say 10"+)

It is only an economical choice where the mirror is pretty big, but the effort required grows rapidly as the wider the mirror the deeper the dip you need to grind in it.

If you do want to make your own, read this o get an iodea of what's involved in a BIG mirror :

stargazerslounge.com/topic/237343-the-22-mapstar-mirror/

SGL is a good place to seek advice whether you decide to grind a mirror or just buy a scope.

Neil

Two main advantages to making a mirror from scratch,
1: you learn a lot of optics.
2: you can make a far better mirror than the ready made ones, but it does take time.

I got my 10" F6 to a 1/20 wave of yellow light, it took over a year.
(can I see the difference between that and an 1/8 wave mirror? very seldom under British skies).

Several coating firms around, Galvoptics and Vacuum Coatings are two;
http://www.scientificmirrors.co.uk/vcsm-Aluminising.html

It used to be worthwhile buying a cheapo scope and refiguring the mirror to better tolerances.

Many astronomical associations run mirror making classes, try your local AS.

Once you've finished your primary then there's the secondary (and its support system). The primary cell to design, a good focusser.........    then the mount......  and so it goes on

Edited By john carruthers on 15/02/2017 08:42:32

Amazon sell an unbelievable number of dangerous chemicals and they will post them. If you know the right components you can even buy them to make your own batch of nitro-glycerin!

If you are going to build your own scope I would advise:-

1. Only do it because you want to enjoy the process not just because you want one. (That applies to steam locos too)

2. If at all possible find a friend (or a younger family member) and make two which will add to the enjoyment and make the journey less lonely. It takes a long time to grind and polish mirrors. My friend Barrie and I did a 12" and a 10" over about 4 months working one evening a week. With two people you can swap over every 5 minutes and of course chat at the same time which speeds things up and adds to the enjoyment.

regards Martin

Thanks for all the advice. Will continue to learn on the little telescope and further investigate what I might be able to make or buy. Am off to have a look at Jupiter and Saturn tonight and not expecting the results to be as fabulous as my initial moon craters.

Bill

You may be surprised...

In my younger days, the standard reference book(s) was (were) 'Amateur Telescope Making' by Ingalls, volumes 1 to 3. I think you could get a long way with mirror grinding and mount design with just volume 1. The other two volumes cover a wider range of associated (& interesting) topics including the home workshop production of optical components for binoculars etc. for the military during WW2.

But I daresay that's a bit passé nowadays.

Best regards,

Swarf, Mostly!

Those books were my bible as well and I still have them, although I gave up astronomy many years ago now.

John

The old fashioned way of silvering was done horizontally using packings to make the glass perfectly level, I worked for pilkingtons for a large part of my working life & our silvering dept used to do it vertically with spray guns using ammonia, distilled water,silvering solution, copper plating & only laying it flat for painting & lead backing,the silverers were secretive about the solutions they mixed for all the beautifull coloured silvering,alas all gone now when pilk's got rid of us all.

Trouble with telescope mirrors is the silvering is actually on the front.

regards Martin

Hi Bill,

I have used the same company as John Carruthers mentioned, VCSM in London, they cleaned and re-silvered two 6" mirrors for my binocular scope and for £10 carried out some optical testing.... Focault test..Knife shift..Focal length..Parabolic figures.. Surface irregularities...Astigmatism pinhole test... Cost in Dec 2015 was £104 for the pair...nb I have no connection with this company.