“Weather or Not” Companion Sheet

WCAC Program

June 12, 2009

Weather and astronomy naturally go together.  A fascination with the sky is the only requirement to be an amateur astronomer, so it’d stand to reason that stargazers often find weather just as fascinating.

Ohio’s stargazers, though, think of their relationship with weather as…um…adversarial.  Here’s some selected links that will help boost your odds of success under the skies.


I.  Satellite Pictures--Yes, they’re a dime a dozen on the internet; where to begin?  My personal preference is this one:  http://weather.msfc.nasa.gov/GOES/goeseastconus.html.  Both visible (higher resolution) and infrared satellite loops are available, and allow you to center the plot.

            Visible satellite loops work best for detecting low clouds during the day.  Infrared satellite loops work best for detecting high clouds and are the only viable option at night.


II.  Light Pollution--Boy, Ohio’s got plenty of that.  A site I’ve used for site scouting is this one:  http://www.jshine.net/astronomy/dark_sky/.  Basically, it’s a combination of the light pollution map you’re familiar with on Clear Sky Chart and Google Earth.


III.  Transparency--Haze is a major impediment to deep-sky observing in Ohio.  Most (but not all) of the haze in Ohio is caused by sulfates emitted from coal-fired power plants.  The two best sites for tracking haze are the GOES Aerosol and Smoke Product (http://www.ssd.noaa.gov/PS/FIRE/GASP/gasp.html) and IDEA/MODIS (http://www.star.nesdis.noaa.gov/smcd/spb/aq/).

            A general discussion on haze and transparency and its effects on deep-sky observing can be found at the following sites: http://www.skyandtelescope.com/howto/visualobserving/19331599.html and


IV:  General forecasting--Well, there’s the ol’ reliable standby, http://www.cleardarksky.com/csk, and it’s proven indispensable to amateur astronomers for almost a decade.  It does have a tendency to underestimate approaching high clouds and overestimate lingering low cloudiness, but overall, it’s light years ahead of a standard NOAA forecast for cloud cover, and offers an accurate forecast for seeing.  Caution is advised if using CSC’s transparency forecast, though, as it only factors in moisture, not aerosols, though the latter play the dominant role in Ohio’s haze.

            A relative newcomer is http://astroforecast.org:8080.  This is similar to CSC, only it goes out over a longer time frame.  Another new kid on the cloud forecasting block is Australia’s Skippy Sky, http://www.skippysky.com.au/. 

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