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The Sky-Glow Story part 2
I have proven that many FCO heads can be as polluting as any classic cobra-head with dropped refractor. In fact in most situations, the manner in which they were installed - replacing a failed classic cobra-head using the same watt lamps - up-light increased with some new FCO heads.
That "15" sticker is a code used by the lighting industry. I supply all the details of this code system. Quickly for now, it indicates the required watt and type of lamp for easy relamping by the technician.
One metal-halide lamp like the one pictured below pollutes like thirty three 100 watt older HPS cobra-heads in a summer urban setting.
The math is simple:
Let's say only half of the light from one 400 watt metal-halide advertising lamp is sky-bound (i.e., 14400 mean lumens of up-light). A classic cobra-head was found to have 5% total up-light in an urban residential setting in summer (with canopy). For each 100w HPS street-light there are 430 mean lumens of up-light (.05 x 8600 lumens) => 14400/430 = 33 !
More to come. Keep checking back! Thanks.