Monday, July 14, 2008

Astronomy in Illinois?

Our astro-geek friends ask us about the observing conditions from our "Illinois Estate". The short answer is that I switch to birding in the summers! Compare the images above for the long answer.

The above images are from the DMSP (Defense Meteorological Satellite Program) satellite's views of the earth, which also approximate the sky brightness or light pollution from various locations on the earth. The top image is of the Chicago area against the shores of Lake Michigan, with alternative "white islands" caused by Milwaukee to the north, Madison, WI to the west of Milwaukee and Rockford between Madison and Chicago. The cross in the center marks the location of Peck Farm Park, a county park about 10 miles from our place in St Charles, where, in fact, the Fox Valley Astronomers actually holds observing sessions.

The lower image is of the Tucson area with Phoenix to the NW and Nogales on the mexican border to the south. The small crosses mark observing locations - either permanent private or public observatories, or even just observing sites. They are from a website called the "Clear Sky Clock", which predicts clouds and seeing conditions for a 48 hour window for customizeable locations:

The two maps appear quite different for a number of reasons. The primary difference is due to population density - there are more people as well as more people/square mile in the Midwest. Also, in the desert Southwest, away from the population centers, you literally find little to nothing in the way of civilization, including lights. Add lower elevations, higher humidity and unshielded "security" lights common thru the Midwest and you get more scattering of the lights that are there.

In addition, Tucson is "dimmer" than similar cities of it's size because it has been a leader in developing lighting codes to limit light pollution because of the national observatory an hour SW of town. As a result, from my house in Tucson just a few miles north of the University of Arizona I can still see the Milky Way when the humidity is low. There is no chance of seeing the same thing from St Charles, where only the brightest constellations are visible.

I'm spoiled by the Arizona skies - an hour's drive will get you to just about the darkest skies possible (visible as black in the Arizona image above). Note that in the Illinois image, there is no blue you can drive to in 2 hours (from map center to the edge), let alone black area with the darkest skies. And yet another bonus, the Midwest has those mosquito thingies that make careful examination thru an eyepiece a difficult endeavor. We won't even talk about the temperatures it can reach in the wintertime - mostly because I'll be headed off to Tucson by November, where even a frigid night barely gets below freezing in southern Arizona.

So while I admire those midwestern astronomers who overcome adversity, I'll switch to birdwatching during those summer months!

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