[magnitude6] viewing the spectra of streetlamps

[Jan Hollan <jhollan@amper....muni.cz>]

just a technical remark:

 The diffraction glasses I had in Lucerne are available either from 
     http://www.rainbowsymphony.com
 or as a last item in the list at
     Linkname: Edmund Scientifics: Optics > Optical Effects
     http://www.ScientificsOnline.com/Products/ListProducts.cfm?catid=288
 -- another gratings are at
   Linkname: Edmund Scientifics: Optics > Other Optics - Diffraction
          Gratings
     http://www.ScientificsOnline.com/Products/ListProducts.cfm?catid=174
  
Thanks to these glasses, I saw the white ``sodium'' light second time in
my life and another ``not completely orange sodium'' the first time ever.
I think that understanding the light sources is an important knowledge in
our efforts to bring the world back to sanity again, and seeing their
spectra helps it. Selling such glasses at observatories might be a good
idea. 

cheers, Jenik Hollan

PS.
 A quotation from my letter written some days earlier:

In August in Austria and recently in Lucerne, Switzerland, I saw the white
sodium lamps really. They were as white as halogen incandescents or the
white CFL. But not bluish like the MH bulbs. The absorption core of a
sodium line has been visible as usual, so the pressure seems to be the
same, but a strong emission band in green has been added (the standard Na
green emission line there has been almost invisible) and some bands in
blue. So, there are some additives, if in the discharge or as a luminofor,
I don't know.

In Lucerne I saw also the yellowish sodium lights. There had just a bit
more orange or yellow hue than standard incandescents. No additives, just
a standard Na spectrum, but a much (thrice?) broader absorption core, so a
higher pressure. The red wing of the broadened main Na emission line is
fainter with respect to a green one (I don't now why), whereas the blue
lines are probably stronger.

So it's true that sodium is never white, but sodium with something added
can be, being probably spoken about again as sodium light. It should have
some other name, however.




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