"Eric Johnson" wrote in message
...

I was thinking you were going to mention the northern lights we've been
seeing here in southern WI for the last few days. Now thats light
pollution

Wow - wouldn't you know it? I leave and they show up...

I grew up with Yerkes Observatory *literally* in my backyard.
(http://astro.uchicago.edu/yerkes/) Was educated about Light Pollution from
an early age...

IIRC - they did say that the adoption of Na lights would make things easier.
Easier, I suppose, to filter out the one wavelngth.