Mirror cleaning

[Zander]

i tried to distill my own. got about 5 mls for about 30 mins work . mebbe i was doin sumthin wrong

[ballaratdragons (Ken)]

Originally Posted by Zander

i tried to distill my own. got about 5 mls for about 30 mins work . mebbe i was doin sumthin wrong

[Gargoyle_Steve (Steve)]

5 mls of water for 30 minutes work doesn't sound great - 5 mls of alcohol, on the other hand ...... that would be a little bit better! You wouldn't waste it on the mirror though if you had that kind of distillation going ok.

back on topic - my local Super Cheap auto accessories place has 4 litres of distilled or demineralised water (not sure which, but it cleans my mirror ok) for less than $4. I haven't seen it cheaper anywhere so far.

Don't use "spring" water - read the label carefully, they are full of various kinds of minerals, etc, and the amunts and types vary hugely from brand to brand.

[jjjnettie (Jeanette)]

Spring water/ Mineral water contain sodium and calcium as disolved solids that will become solids again once the water evaporates.

[Satchmo]

Don't leave any water on your mirror to evaporate. Dab it off with cotton balls or a bunch of kleenex tissue. I've got an 8" overcoated mirror here thats been cleaned and rinsed under the normal tap for 15 years and it still looks perfect.

[ausastronomer (John Bambury)]

Originally Posted by Satchmo

However a bare aluminium coating will form a hard layer of Aluminium Oxide on top within 3 months which is pretty strong.

It might be pretty strong, but it still doesn't last very long. The majority of front surface mirrors in professional observatories are bare aluminium coated, not overcoated and need to be recoated about once a year. Overcoated aluminium usually lasts between 5 and 25 years depending on use and environment.

CS-John B

[Satchmo]

John, I was referring to resistance to scratching after three months rather than ultimate longevity of plain aluminium . It depends very much on how clean the mirror has been kept and where the scope is used. I have seen plain aluminium mirrors that have been kept covered , in remarkeable condition after 10 years. I wouldn't however recommend anybody to get a plain alumium coating mirror these days, no matter how `exotic' a vendor might claim there coating to be.

Originally Posted by ausastronomer

It might be pretty strong, but it still doesn't last very long. The majority of front surface mirrors in professional observatories are bare aluminium coated, not overcoated and need to be recoated about once a year. Overcoated aluminium usually lasts between 5 and 25 years depending on use and environment.

CS-John B