Re: [ATM] wire spider, and regular spider, reason not to blacken

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

Mark, list

Long time ago, in physics school, I've learned that for a certain wavelength
the coefficient of emission is equal to the coefficient of absorption!

> Shiny is best for night time.  Solar observation on the other hand has to
deal
> with equipment absorbing too much infrared from a small bright source.
Here,
> you want low absorbtivity, but high emissivity.  White is usually best,
even
> better than polished metal.
>
>                  Absorbtivity     Emissivity
> White                low             high
> Black                high            high
> Polished metal  moderate - low       low

Conservation of energy requires that the sum of coeffcients of reflection
and absorption is 1.
Polishing a surface minimizes the effective area, and therefore (for a given
absorption coefficient) minimizes the total amount of absorbed energy.
A polished surface that has a low emission/absorption coefficient in the
infrared side of the spectrum will give best results.

You can also refer to Hyperphysics, which is a very handy site anyway:
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c1

Also see:
http://www.electro-optical.com/bb_rad/emissivity/emisivty.htm

Arjan te Marvelde

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