Here's a letter I wrote to the Chancellor and others at a local university, who had installed searchlights to advertise performances at their performing arts center. The University kindly wrote back and said they would mend their ways by limiting use of the searchlights to more reasonable times before a performance begins, and making sure they are turned off just as soon as the performance begins. I do believe they were as good as their word--there have been no more complaints. Names deleted so that nobody is embarrassed.
I am writing concerning the searchlights that have recently been installed atop the XXXXXXXXXX Performing Arts Center.
I am an amateur astronomer and a semi-retired attorney. As an amateur astronomer, I am concerned about light pollution issues. Amateur astronomers come in many flavors, from casual star-gazers, to highly engaged deep sky observers and astrophotographers, to hard core spectroscopists. Aside from cloudy nights, the biggest problem faced by amateur astronomers in this area is light pollution. You might be interested in seeing the light pollution map of the southeast area of XXXXXXXXXXXX which I enclose with this letter. This map, a standard astronomical tool used by most amateurs, dates to 2015. Basically, astronomy is impossible in the purple area, only the very brightest celestial objects can be examined in red area, and useful astronomy only begins to be possible in the yellow area.
The University XXXXXXXXXXXXXXX is of course a contributor to light pollution with its parking lot and other lights. These point sources, however, are generally directed downward and are likely no worse than normal city lights. Their light output doubtless contributes to the light pollution shown on the 2015 map, but turning them off entirely would probably have little effect.
The searchlights, however, introduce an entirely new type of light pollution, one that extends well beyond the area depicted on the map. These lights are directed upward and significantly degrade what astronomers call "seeing conditions" for many miles around. Indeed, press reports say that the searchlights are 1.7 billion candlepower each. A review of advertising literature for such searchlights shows that they are visible up to 28 or even 40 miles away, which is consistent with what people are telling me of your lights. This means that seeing conditions can be degraded to the same extent.
While I live on the far west side of XXXXXXXXXXXXXXX and can conveniently do my observing out in rural sites between XXXXXXXXXXXX and XXXXXXXXXXX, many of my fellow hobbyists in the XXXXXXXXXX Astronomical Society, especially those with fixed observatories, are not so fortunate. Viewing is degraded, and astrophotography and spectroscopy are nigh impossible for them to perform while the searchlights are on.
As an attorney, I believe that your searchlights violate, among other things, Section XXXXXXXXXXX of XXXXXXXXXXXXX's Code of Ordinance, which provides in relevant part with respect to site lighting (italics added):
(3) General standards.
(i) Site lighting shall include all lighting on property, other than lighting within a fully enclosed building.
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(iv) Site lighting shall not result in light trespass by spilling over to adjacent sites or properties.
* * *
(vii) Except when displaying the flags of the United States of America, State of Illinois or City of XXXXXXXXXXXXXX or as may be provided elsewhere in this section, site lighting shall at no time be directed upward (up lighting), in a radiating pattern and/or moving or sweeping pattern, or at any angle which will light surfaces other than building walls, parking or pedestrian areas, and landscaped area, and shall not create lighting patterns which will direct light toward residential areas.
But aside from all that, it is just plain unneighborly to have such lights. Several of my friends who have no interest in astronomy but have seen the lights far to the south of XXXXXXXXXXX have remarked on that point.
I'm sure that XXXXXXXXXXXXXXX had the best of intentions in installing these lights as a way of advertising various events to be held at XXXXXXXXXXXXX However, for the reasons stated above, I respectfully suggest that this was a mistake, and I ask that XXXXXXXXXXXX reconsider its decision.