on 5/4/02 6:27 PM, Winsor Crosby at wincros@xxxxxxxxxxxxx wrote:
>> I think you mean mercury vapor, right? Mercury vapor lamps are greenish,
>> while the ubiquitious sodium vapor lamps are that horrible shade of
>> orange.
>>
>> Mark Marr-Lyon
>
> I guess it is subjective, but mercury vapor lamps look blue to me
> which is confirmed by
> http://isaac.exploratorium.edu/~pauld/summer_institute/summer_day9spectra/spec
> tra_exploration.html
>
> There are different sodium vapor lamps, the low pressure that look
> orange and the high pressure that look yellow. I have never seen the
> orange ones. The yellow ones which are the choice of the city I live
> in, at least to me, appear to have a pronounced greenish tinge which
> makes them particularly hideous.
> --
> Winsor Crosby
> Long Beach, California
>
> ?
In San Jose, the city code requires the orange sodium lights, to accomodate
the Lick Observatory (which is still hamstrung by light pollution...) I
understand the astronomers use a very narrow bandwidth filter to block out
the effects of the orange sodium light, which has actual light energy only
in a few narrow parts of the spectrum. There is unfortunately no way to get
all the lighting outdoors to be this orange sodium lighting, so the
astronomers are fighting a losing battle with light pollution around here.
A few years back I stayed with a couple friends at the family's 'ranch
house' off the the depths of the California central valley. We were riding
motorcycles, at the races at Laguna Seca, and the house was about 25 miles
inland and down the 101 freeway. We left the festivities on Cannery Row at
about midnight, and after an exit from the freeway, about five miles of
pavement and another two miles or so of dirt, the last half-mile of it not
even a road, we pulled up at the 'ranch house'. This was about 1AM, and we
shut down the bikes, turned off the ignition (which shut off the headlights)
and then I pulled off my helmet... I almost fell over backwards! I had NEVER
seen so many stars...! The full Milky Way spanned the sky, I think we city
boys stood there for about five minutes with our heads back just staring...
You can't see much of anything around here by comparison... We could see the
star colors, and it was magnificent. The nearest source of any light
pollution at all is Soledad prison, about 15 miles away. BTW, the house was
about 3000 square feet four bedroom, a modern suburban house, just out in
the 'middle of nowhere'.
--
Jim Brokaw
DoD #1415 SOHC/4 #40 AMA #716223
Santa Clara, CA
_________________________________________________________
1978 CB550K - First Bike 1978 CB750K - Big Brother
1980 CB750F - Money Pit 1994 VFR750F - Fast Bike
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