resilvering mirror?

magicbastarder

i have rescued an old dobsonian, which was originally purchased in 1997, from storage (where it's been for over ten years), and looking at the mirror, i think it needs more than a simple clean - there are spots on it which look like tarnish.

is there anywhere in dublin which can recoat the mirror? it's an 8.75" mirror, was bought from astronomy ireland, and didn't get much use due to me having lived in phibsboro without owning a car, and not enough space to store it at home anyway.

Kersh

There is nowhere I know in Ireland that does recoating.


http://www.galvoptics.fsnet.co.uk/telescope.htm in the UK do it.

As do http://www.orionoptics.co.uk/OPTICS/mirrorrecoating.html

Hope this helps

dbran

Hi

Have you actually tried giving the mirror a clean most of it could be down to dust. If there are only spots on the mirror where the coatings have degraded it still may not have a huge effect on the optical quality. So have you actually tried to look through it.

Getting the mirror recoated would be very expensive and the last resort given the price of new good quality dobsonians on the market now.

Best Regards

dbran

magicbastarder

cheers - that was after a clean, you can see spots of slight discolouration in the surface which are not surface dirt or dust.
i have looked through it and it still works OK.

dbran

Hi

If it is just some discolourations in the coatings this may be just part of the original manufacturing process especially if you are using a flashlight to do the test.


Best regards


dbran

Seanie M

My own 2 cents worth: be careful about cleaning a telescope mirror. The nature of the coating makes it easily susceptible to be wiped off the glass surface if not treated correctly.

I have used a tablespoon of washing powder in hot water to get it completely dissolved, then when cooled place the mirror silver side-up in the basin and leave to soak for no more than 30 minutes. The amount of water in the basin should be enough to cover around 2 cm above the mirror surface when placed flat in the basin. do not re-stir the water prior to and after placing the mirror in it.

If wiping is needed, a camel hair brush is recommended, but do not use circular motions - treat it like a CD, and wipe very gently from the inside radially outwards at a slow pace while flat in the water. Do not overwipe the surface if you can help it.

Then place it in another empty basin, angled almost upright on a prop like a piece of wood or hard rubber mount of some kind (around 2 inches from the bottom of the basin), and rinse off with distilled (NOT tap) water. Leave propped at an angle to ensure all water droplets run off. You can use a hairdryer on its coolest setting to coax the water droplets off and speed up drying time.

It's not a perfect method, but it is one of the best. If the coating is poor and begins to fall off during the rinse phase, then its time to get it coated and would not have been saved anyway.

Also, I have used Orion Optics a couple times on various mirrors in the past and would give them my recommendation.

Hope this helps,

Seanie.

michaelotoole

From asking around this video seems to fit the bill... The purists around might suggest using distilled water for the whole process especially the section involving wiping with the cotton wool as on occasion tap water may contains some grit partials...

Link: http://youtu.be/8TObET2F-EA
Mike