There’s a five-year difference between the left side and right side of the picture. That’s the period when the city if Dunedin in New Zealand changed its sodium lights to shielded LED lighting.
The effect: less light pollution for animals, a more visible nightsky for people to admire. The two photos below were taken by amateur astrophotographer Brad Phipps five years apart, with the same camera (Sony a7S Mk1), the same lens (Sony 16-35mm), the same camera settings (16mm, ISO 2000, 8″ exposure, F4) and at the same location.
Clearly a win-win sitation…except for astronomers. While telescope sodium filters are designed to block out the sodium yellow, and allow the starlight through, the new lamps produce light including the same wavelengths as starlight. This could make astronomers’ work somewhat more difficult.
But hey, aren’t a few thousand people being able to see the stars at night more important than maybe a couple of astronomers who are active in the area? Also, the new lights are shielded, which means the light doesn’t go up, as in the case of the old sodium ones. So after all, the change might not affect even astronomers that badly.
Just look at the difference.