Light Pollution Abatement Site Calgary Centre Royal Astronomical Society of Canada

Color	Artificial/Natural Sky Brightness	Sky Brightness mags/sq arcsec	Description (Courtesy of Russell Sipe)
	< 0.01	> 21.6
	0.01 to 0.11	21.6 to 21.5
	0.11 to 0.33	21.5 to 21.3	Long exposure astrophotos might show some light pollution gradient, but visual observing is relatively unimpaired.
	0.33 to 1.0	21.3 to 20.8	Modest impact on deep sky observing and imaging. Milky Way shows structure
	1.0 to 3.0	20.8 to 20.1	Serious impact to deep sky observing and imaging. Milky Way visible but not crisp.
	3.0 to 9.0	20.1 to 19.1	Milky Way not visible
	9.0 to 27.0	19.1 to 18.0	Less than 100 stars visible over 30 degrees elevation
	>27.0	<18.0	Hopeless?

This image extracted from the World Atlas of Artificial Sky Brightness, produced by:

P. Cinzano, F. Falchi (University of Padova), C. D. Elvidge (NOAA National Geophysical Data Center, Boulder).

Copyright Royal Astronomical Society. Reproduced from the Monthly Notices of the RAS by permission of Blackwell Science. Data courtesy of the Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso (Light Pollution Science and Technology Institute) of Thiene, Italy www.istil.it.

For information about this map and the World Atlas of Artificial Sky Brightness, visit www.lightpollution.it/dmsp/ or www.inquinamentoluminoso.it/dmsp/