Ranking light pollution

DK
From: David Knisely
DK
Subject: Ranking light pollution
DK
Date: Thu, 24 Jun 2004 23:39:59 -0500
DK
DK I would say that this is probably in the moderate category of light pollution.
DK There are worse, but there are also considerably better conditions.
DK I came up with an idea of gauging sky quality a while back which divides it
DK into several levels: Severe, Moderate, Mild, Dark Sky, and Pristine. I would
DK call Severe light pollution a situation where (even in the absence of direct
DK lighting), only stars magnitude 3.5 and brighter were visible to the unaided
DK eye with considerable skyglow in all parts of the sky. Areas like some places
DK in New York City or central Los Angeles could fit this classification.
. . .

There are certainly places in the City with Severe light
pollution! i do not negate that statement. I've tried viewing from
some of them over the years, and, uh, it's tough.
However, there are many places within the City that njoy moderate
light pollution, of the sort associated with outer suburbs, even tho
they are among the densest districts on Earth. Transparency in these
places is 4.5 magnitude and on the best of night it descends to 5th.
An intermediate refion is manhattan, where for about 25 years I ws
privileged to mind my ladylove's rooftop flat. Surrounded by some
50,000 inhabitants per square kilometer[!] I could see the
characteristic stars of the constellations, several stars in the
Pleiades, the glow of the Beehive and Coma clusters and sprinkling of
stars in the north galactic pole region (when overhead).
The trick in general is to get local lights out of your face. One
way is by shields, like walls, alcoves, portable folding panels,
standing in a large refrigerator box (at least no one bothers you).
The other is by elevation above the light line, 6 to 10 meters off
of the street. The flat I mentioned was only nine floors up but there
were very few direct lights shining on to it, making the sky actually
quite dark and comfortable to watch.
Other possibilities are hilltops, cliffs, glacial moraine,
building terraces, el platforms[!].
Eith some patience and without being spooked by the glitz of some
magazine and book pictures, you can appreciate skywatching from New
York.

---
þ RoseReader 2.52á P005004