For some time I've wanted to come up with a way to clearly illustrate the effects of light pollution Champaign-Urbana on "rural", "dark site" astronomical observing locations used by the local astronomy clubs. I finally had an ideal opportunity to take a photographic panorama for this purpose recently, and the sequence of images below are the results of my first attempt at capturing the situation photographically.
My main goal is not to belabor the fact that we have some light pollution, I think a small amount of light polllution is unavoidable. My main concern here is to clearly illustrate that the light pollution from Champaign is already of such a magnitude that it compromises astronomical viewing conditions in rural locations several miles outside of town. The panorama clearly shows how the light domes over Champaign and Urbana wash out the stars in the northern half of the sky from this observing location. Full details about the camera and exposure settings I used are listed further down on this page.
John Stone, 4/4/2005
I took this sequence of pictures at the "first light" for the newly refigured and rebuilt 16" CUAS classical cassegrain telescope at the "dark site" location used the CUAS and UIAS astronomy clubs on April 2, 2005.
The sequence of images begins facing due North, with image 779 and continues in a clockwise fashion through East, South, West, and back to North. This sequences of pictures was taken between 10:10pm and 10:18pm, so there should be minimal variance in lighting or atmospheric conditions. The panoramic image sequence was taken using identical 20 second exposures at f/2.8, with a 20mm wide-angle lens on a Canon EOS 350XT digital camera set at ISO 1600. (1.6x magnification ratio compared with a traditional camera body for 32mm equivalent focal length) I chose the exposure time to be short enough that the stars wouldn't trail much, and so that the exposure depth yielded images that closely resembled what a typical observer with fully dark-adapted eyes actually sees. I stopped the lends down to f/2.8 to gain a bit of sharpness in the star images.
Each of the original full-resolution images was taken at the maximum camera resolution of 3456x2304, and subsequently scaled down to 1152x1728 and to thumbnail size for presentation on the web.
The tripod was as level as I could manage in the dark, and I tried to make sure that there was enough overlap in each image to allow subsequent image registration and stitching so we can make a single-image panorama with a bit more work. Nevertheless, even this simple sequence of images clearly illustrates the light pollution conditions several miles from the city. The light domes from Champaign and Urbana to the North are by far the most visible, though smaller domes can be seen in the South towards Tuscola, and to the West towards Monticello and Decatur.