Theres always two ways of looking at something and from the literature and design guildlines I've read, Sodiums reduce crime because the yellow light discomforts people making them less likely to linger around the area. Insects are also repulsed by yellow light so maintaining and cleaning the light fittings can be performed less regularly than mercury vapours.

Leds are good not just for observatories but around airports as well since the upward spill from normal lights needs to controlled using aeroscreened fittings. To pilots a straight row a streetlights can look like a runway.

(oops make that eight)

USB 7.0: Ridiculous-Speed!