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The Sky Brightness Map is based on work by Cinzano, Thiene, Italy
(1998). It is color coded according to the Bortle scale. The site
is located in the gray area which is a rating of 2 on the scale
and has a limiting magnitude of 7.1-7.5. You can clearly see that
the chosen area is indeed the darkest available in Southern Canada.
The site is indicated with the red circle. In August 2010 a reading
of 21.69 was taken at the area with Cygnus overhead, thus about
21.90 removing the effect of the Milky way (0.11 mag).
The map is courtesy Google Earth with the sky
Brightness Map overlaid, pan over the light bubbles to identify
cities and towns.
50 km inner circle and 130 km outer circle, pan over to identify
cities and towns.
Sky brightness table
The sky brightness map is color coded to represent the apparent
sky brightness. White is the centres of large cities while black
(transparent) is for remote areas. The magnitude/square arc-sec
scale is used for measuring the sky brightness. A 22 mag/sq arcsec
reading would be equivalent of 22 magnitude star in a 1 arcsec
area of the sky. The site is to be located in the darkest available
area in southern Ontario, a dark peninsula located near the small
town of Denbigh. This area is in the gray and rates 2 on the Bortle
scale with limiting magnitude of 7.1 to 7.5. The apparent sky
brightness is between 1% and 11% brighter than the natural background.
In addition light bubbles can be seen on the horizon. Ottawa
is the most prominent of these reaching a maximum height of 10
degrees above the horizon. In addition very small light bubbles
can be seen from Smiths Falls + Perth, Eganville, Barry's, Killaloe
Station, Toronto, Bancroft and Renfrew. These are quite small
reaching from 1 degrees to 2 degrees in height. The site is offset
to the north by 20 Km to favor the southern sky for the best view
of the Milky Way, indeed the southern horizon is perfectly black
from the southwest to the north east, more the 150 degrees of
the sky.
Next: Light Bubbles
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