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    RES: Dark Sky Week
    From: José Otavio O. de Almeida
    Date: 2004 Apr 19, 09:07 -0300
    Very good initiative. And yes, very much related to celestial navigation. Another usefull link: http://skyandtelescope.com/resources/darksky/
    -----Mensagem original-----
    De: Navigation Mailing List [mailto:NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM]Em nome de Frank Reed
    Enviada em: segunda-feira, 19 de abril de 2004 01:37
    Para: NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    Assunto: Dark Sky Week

    A few comments regarding light pollution and dark skies... (this is very peripherally related to celestial navigation, but since "National Dark Sky Week" starts tomorrow, I think it's worth the diversion):

    Fred H wrote:
    "Just to ride this hobby horse a bit farther, I don't see why street
    lights can't be capped with reflectors so that the light goes down, but
    not up, and also doesn't go sideways very far.  It would save quite a
    bit of electricity, due to doubling of the light output on the target
    from the reflector, and reduce light pollution.  It wouldn't be that
    difficult to implement, and would be reasonably cost free."

    True and many towns do just that. There are legally binding ordinances in many areas requiring just the sort of shielded downward pointing lighting you're describing. But public lighting is only part of the problem. Drive down any street in any town and you will see bright lights blazing from businesses and private homes and more of them every day. This is advertising at work. Businesses and individuals alike proclaim their success by lighting up the night. In addition, it turns out that ordinary people generally *like* artificial lighting at night. People are scared of the dark. <g>

    Coincidentally, National Dark Sky Week begins tomorrow (national = US... maybe someone will think to rename it "international" if the movement is successful). You can read about it on space.com today and at darksky.org.

    Gordon T wrote:
    "A few years ago, my family and  I took a trip to Death Valley
    out in the desert here in California. I was astonished at the
    stars visible on a clear night without the interference of the
    lights of Los Angeles. At the Grand Canyon in Arizona a few years
    later it was the same."

    Yes, it's impressive, isn't it? You don't have to go that far to find dark skies. Almost every major city has a dark zone within an hour's drive. If you want to find one, ask yourself, 'where is the most undeveloped area near my town?' National parks and especially national forests are prime candidates.

    And wrote:
    "I can certainly see how some star that "cannot" be seen now with
    the light pollution, could very well have been seen without difficulty
    in the past."

    Absolutely. Major observatories were once located in or very close to major cities: Greenwich is close to London, the US Naval Observatory is in Washington, DC, etc. Now you have to "drive to dark" as I call the ritual if you want to see the sky the way it's supposed to be.

    But there's another piece of this puzzle to keep in mind... what we might call "indoor light pollution", to coin a silly phrase. Have you ever wondered what the stars would look like if you were aboard a spacecraft, maybe travelling to Mars? In science fiction movies, the stars look spectacular through the windows, like christmas tree decorations (and in older sci-fi movies, that's exactly what they were!). But that's highly misleading The view of the stars depends not so much on being in space but on dark adaptation. Is it dark in your spacecraft? Has it been dark for 30 minutes or more? If not, your view will be poor. It's very much the same thing as viewing the stars from inside a well-lit cabin on a mountaintop down here on Earth. The air at high altitude has almost no effect on star brightness so your view should be almost exactly the same as the view in deep space (we are *in* deep space, after all). But if you look out the windows from a well-lit cabin here on Earth, you'll be lucky to see even one bright star. You have to turn out all the lights and keep them out long enough to dark adapt. If you want to experience the night sky the way it might have been for Lewis & Clark or the way it would be far out in space, you have to get away from other people's lights, *and* you have to turn out your own lights to allow the irises in your eyes the opportunity to expand so that they can collect all those rare photons from the faintest of the stars. It's amazing how much difference it can make if you spend time in the dark before you step outside to look at the night sky.

    Frank E. Reed
    [ ] Mystic, Connecticut 
    [X] Chicago, Illinois 
       
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