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A comment on Chicago's About to Get a Lot Less Orange. Parent comment

Re:Chicago's About to Get a Lot Less Orange by bsder on Friday April 21, 2017 @09:50PM (#14170718)
LED will pretty much be better in terms of light pollution. With tubes or filaments, you need to make expensive reflectors to prevent the light going in directions you don't want.

LED lighting is much easier to make directional. With LED lighting, the difficulty is making it more isotropic.

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Re:Chicago's About to Get a Lot Less Orange by colanderman on Saturday April 22, 2017 @12:18AM (#14171094)
Sodium lights are trivial to block using optical filters. This is very common in astronomy.

LEDs + phosphor, not so much, due to their wider spectrum. That less is emitted directly skyward doesn't help if what's reflected off pavement can't be filtered out. (Pavement is surprisingly reflective even though it's "black".)

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