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"Martin R. Howell" <> wrote
...
> On Thu, 06 Apr 2006 22:14:57 -0600, Shawn wrote:
>
>> I have three dark sites, one very close
>> http://cleardarksky.com/c/StnBrCOkey.html
>> The other two a bit farther away, but darker (which is saying something!)
>
>
> I think the magnitude readings on the Clear Sky Clock are a bit misleading
> if not just plain off. For instance, I live about 8 miles east of
> Everett,
> Washington which is a city of an 80,000 population and is also just about
> 27 miles north of Seattle, Washington (with a metro of over 3 million).
> Here is a link to the Everett CSC:
> http://cleardarksky.com/c/EverettWAkey.html?1
>
> Notice that it too shows 6.1 skies for a period of time like your clock
> does. And I know that the Everett readings are just plain wrong because
> here in Lake Stevens (again, 8 miles away from Everett), I live away from
> even its "core" and on a fairly dark street. The best NELM I can achieve
> is perhaps 5.1 to 5.3 on a GREAT night.
>
Martin,
Unfortunately I think that some of the urban area light pollution is
growing and covers a larger area than what the ClearSky Clock maps show. I
would bet that if a site is near a "color" border and is close to a large
urban area, the light pollution had bled outward. On the other hand I have a
rural NY home and a second home in the Adirondacks. ClearSky show my primary
home on a green/blue edge and it's pretty dark, but noticeably darker just
10 miles away at a friend's house. My Adirondack place is in a totally
'black' zone and it sure is dark. M-33 is a naked eye object and the only
way you know a cloud is passing is that there are no stars in a patch of
sky. There is not enough ground light to illuminate the bottom of clouds at
all and there are no light domes in any direction.
George N
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