wrote:
The latest locale to join Toronto and Raleigh in the LED City
initiative is none other than the home of the Wolverines, which
recently announced plans to replace about 1,400 street lights with
light-emitting diodes. The city is claiming that it will be the
nation's first to "convert all downtown street lights to LED
technology," and it's hoping to save around $100,000 per year in doing
so. Not surprisingly, Research Triangle Park-based Cree will be
providing the components for Ann Arbor's transformation, and it sounds
like it'll take a couple of years before the $630,000 project is
actually completed. Hopefully, it won't take quite that long before
the Maize and Blue can topple Ohio State again.

Taken from
http://www.engadget.com/2007/10/19/a...ced-with-leds/
where there are other links

Is this going to be good or bad for clear skies ?

Well, LED's only work with one polarity (all diodes work like a one way
valve, letting current flow one way but not the other) so on alternating
current they will flicker at the same frequency as the mains (50 Hz in the
UK i think) which means there are 25 periods of darkness per second.

Could this mean we could use mains current as the clock to phase CCD's so
they are only "on" when the LED street lights are off. If whole cities are
LED lit we could, by phasing our light capture periods with the LED nulls,
have a huge improvement in the results we couyld acheive in built up areas.

Les

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Les Hemmings a.a #2251 SA