Re: [ATM] How to test a mirror blank?

[Dale Eason <atmpob@yahoo.com>]

Thanks David,
I had always wondered about my conclusion.
Dale Eason

--- David Nicholls <dcn@dcnicholls.com> wrote:

> Dale Eason wrote:
> > That may work, however I once pointed an IR
> > thermometer at the sun and was surpirsed to
> discover
> > that it was about 65 deg F on a warm summer day. 
> That
> > is when I realized that the sun emits very little
> IR I
> > think the sun emits much higher frequency
> radiation. 
> > What I was measuring was the sky temp.
> > 
> > Dale Eason
> 
> The sun does put out a lot of IR, but it's only 1/2
> a degree wide, 
> probably less than your thermometer view angle.  The
> radiation 
> temperature of a clear sky is typically 20 deg C (36
> deg F) lower than 
> the ambient air temperature.
> 
> The H2O and CO2 absorption bands take big bites out
> of the solar IR 
> spectrum, so you'd be viewing the middle atmosphere
> temperature for some 
> parts of the IR spectrum.  Not a simple problem!
> 
> DN
> 
> 
> -- 
> _________________________
> David Nicholls
> http://www.dcnicholls.com
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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