Downward-facing, low pressure sodium lamps [1] used to be quite common in areas near major telescopes, as they are mostly monochromatic; for these, I don't thin

Downward-facing, low pressure sodium lamps [1] used to be quite common in areas near major telescopes, as they are mostly monochromatic; for these, I don't think they were specifically designed for these areas, as much as they were an older lamp type that, when it was realized that newer lamps (eg, high pressure sodium) would be much harder to filter, ended up continuing to be used. It seems that, likely because there is so much experience developing methods to filter out light from LPS lamps, LED replacements have now been specifically designed to mimic them. San Diego used to have many of these, apparently because of Palomar. There are a variety of arguments about safety and especially perception of safety that often leads to them being replaced with brighter, non-monochromatic lamps, though, depending on the political clout the telescopes have in the area. [1] https://en.wikipedia.org/wiki/Sodium-vapor_lamp#Light_pollution_considerations https://en.wikipedia.org/wiki/Sodium-vapor_lamp#Light_pollut...