[ATM] The standard aluminium coating: How much scatter?

["Guntram Lampert" <glampert@aon.at>]

Hello list,

my name is Guntram Lampert. I am an ATM living in Austria, Europe. This is my first posting on this remarkable list.
    It has long been suspected that light scatter originating with the mirror coatings causes a noticeable decrease in image contrast. Though I did search the literature and the internet, and asked knowledgeable people, I rarely got hard facts. The information that did turn up was confusing at best: Trustworthy Texereau says, in short, hardly any scatter, and backs this up(p. 284), some authorities, either in optics or in the coating business in Europe and the U.S. say just the opposite: Much more scatter than even caused by complex multicoatings used for lenses, not too difficult to see.
    So: How much of the incident light is scattered by a well made, standard Al coating, with SiO overcoat? Is there a narrow angle scatter component?
I´m aware  that the properties of even standard coatings differ considerably, and I would be happy even for a good "order of magnitude" estimate, or a reference to the literature.


Thank you!

Regards,

Guntram Lampert
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