Re: [ATM] silvering vs mercury

[Saqib Sajjad <saqibsajjad@yahoo.com>]

actually i wanted to convert my back surface 4" mirror
into single surface mirror because maybe it will give
some results as i am too desperate right now to see
mars on its close pass.

fellow atm Paul Bradley pointed to me to this resource
http://www.atmsite.org/contrib/Coslo/silver/
and i will use this as last resort if everything
fails.

havent found any vendor who does vacuum coating yet
but i have heard that there is a vendor who uses(not
sure yet) electrolysis for coating.

Saqib


--- Ken Hunter <atm_ken_hunter@yahoo.com> wrote:

> Saqib...
>  
> Silvering is possible at home and can be fairly
> dangerous as well as dificult to get good results.
> The silver coating must be deposited by
> precipitation, burnished (polished) without
> scratching or changing the figure of the glass but
> Mercury IS NOT used as a mirror coating.
>  
> Typically, an Aluminum coating is deposited (by high
> tempreature evaporation) on the glass which is very
> clean and processed inside a vacuum chamber. The
> coating is only a few molecules thick and does not
> effect the figuring of the glass enough to matter in
> all but the most demanding applications. If you have
> access to a college Physics professor, he should be
> able to tell you more about the procedure or you can
> join my other Group on Yahoo called VacuumX for
> discussions on vacuum coatings.
>  
> Your vendor cannot know enough to do the job for you
> if he is telling you that he will use Mercury or
> that the coating will change the figure. Please do 
> not commit yourself to any vendor until the books
> arrive and you have a chance to read about the
> processes.
>  
> Ken Hunter
>  
> 
> 
> Saqib Sajjad <saqibsajjad@yahoo.com> wrote:
> hello,
> 
> 
> which coating should be preferred? silver or
> mercury?
> if i chose silvering then it will be done in home by
> me(no experience yet) while mercury coating will be
> done by a vendor.
> 
> 2nd question, when we coat a concave mirror then
> doesnt it sagitta changes? and hence the focal
> length.this is the thing the vendor said he will not
> be responsible for.
> 
> 
> Saqib
> 
> 
> 
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