[rollei_list] Mirror Coatings
- From: Marc James Small <marcsmall@xxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx,<rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 04 Mar 2010 01:04:40 -0500
At 12:43 AM 3/4/2010, Richard Knoppow wrote:
> Note that coatings can also _increase_ reflection and
>such coatings are commonly used on mirrors. For example, an
>aluminum mirror has wider bandwidth than a silver one but
>has lower reflectance in the visible range. By applying a
>coating the reflectance of the aluminum can be brought up to
>an even high level than the silver and the combination still
>retain the mechanical toughness and resistance to oxidation
>of the aluminum. Many other substances have become practical
>for mirror use through the same thin-film vacuum coating
>technology used for lens coating. Plus it is used for the
>production of a wide range of electronic devices.
Only to a degree. In large measure, this was a
marketing ploy by US and Japanese manufacturer's
of amateur telescopes in the 1960's, when the US
amateur astronomy community was unhappy with
aluminium coatings. It has pretty much been
rebutted within that community today, and many
amateur telescope makers have reverted to silver coatings for visual work.
Marc
msmall@xxxxxxxxxxxx
Cha robh bàs fir gun ghràs fir!
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