A lesson from lighthouses on light pollution:
A hometown friend of mine asked me (jokingly) if I ever turn the beacon off for star-gazing. Well, of course not, for obvious reasons, especially obvious to commercial cargo vessels trying to navigate the narrow river channel at night. Even so, it’s not necessary to turn off the light in the tower to see the stars in the sky. Amazingly, the beacon doesn’t interfere with star-gazing. The lamp is fitted with a fresnel lens which shines the light outward on an even plane to be visible to ships but not up or down which would be a nuisance. If only other outdoor lighting was similarly focused so as not to create annoying light pollution…