Even outdoor lighting is not without problems, especially two recent trends are worrying:
- shift from low-pressure sodium lamps (which emit 95%+ of light in the narrow peak, so are a bit easier to filter out in astronomy application, and also don't trigger blue-light neural response in humans, and animals alike) to LEDs (which pollute across the visible spectrum, with plenty of blue light component);
- as light efficiency increases, people often choose to utilize it to increase lighting intensity within same electric power budget, rather than keep same output in lumens, and save some power.
My village recently switched to LED street lamps, and I hate them. The light pollution has definitely become worse here over the last ten years. The village lights switch off around 1am, but that doesn't seem to make a jot of difference to my astrophotography, because the town 4 miles to the South and the city 10 miles to the North keep theirs switched on.
I really missed the sodium lamps after my university "upgraded" to LED. There was something peaceful about the monochrome, and their gentle whine when they got too old.
- shift from low-pressure sodium lamps (which emit 95%+ of light in the narrow peak, so are a bit easier to filter out in astronomy application, and also don't trigger blue-light neural response in humans, and animals alike) to LEDs (which pollute across the visible spectrum, with plenty of blue light component);
- as light efficiency increases, people often choose to utilize it to increase lighting intensity within same electric power budget, rather than keep same output in lumens, and save some power.