OPACITY RESOURCES

Please click on any of the links below.

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US Environmental Protection Agency
http://www.epa.gov/

ASTM International
http://www.astm.org/index.shtml

Source Evaluation Society
http://www.sesnews.org/

Air Waste Management Association
http://www.awma.org/index.html

National Oceanic and Atmospheric Administration (weather)
http://www.nws.noaa.gov/

United States Naval Observatory (sun altitude and azimuth)
http://www.usno.navy.mil/

National Geophysical Data Center (declination)
http://www.ngdc.noaa.gov/seg/geomag/jsp/Declination.jsp