In writing this essay, my intention was to be as thorough as possible and include a spectral analysis of sky-glow. The spectral discoveries I made grew large and seemed important, so I decided to create the second ebook, which was actually finished first. This was "The New Sky-Glow Spectra" which can be found on this page.
Here in The Sky-Glow Story I've tried to show the history of outdoor lighting and its connection to the evolution of sky-glow.
Light-Pollution had a head start with arc-lamps. Here is a night scene for a snowy Detroit street, circa 1900. Early arc-lamps were typically extinguished by evening's end (as the rods were consumed, an arc couldn't be sustained).
The incandescent "White-Ways" of main streets were probably the first permanent dusk-to dawn sources of sky-glow. These images are part of an article titled: "Street Lightng in South Bend, Ind.", by Eli F. Seebirt, Mayor of South Bend, which appeared in the March 1926 issue of the defunct magazine The Amercan City.
Light-pollution as we identify it today was born in the 1960s with mercury lighting. This is when the Milky-Way completely disappeared from all cities and their suburbs. In the mercury-vapor era (around 1960 through 1980), light-levels everywhere increased a minimum of 3x the incandescent levels. Click for larger..
Then came the sodium (HPS) era. A dreadful period for astronomers because that orange sky-glow was very difficult to filter out with nebula (LPR) filters.
Many full-cutoff (FCO) heads were as polluting as the classic cobra-heads with dropped refractor. In fact, the manner in which they were installed (using the same watt lamps), up-light increased with many new FCO heads. Click for larger..
Look at the lux-levels beneath each type of head. Notice the near three-fold increase below the full-cutoff street-lights? That "15" sticker is a code used by the lighting industry for quick relamping by a technician. I supply all the details of this code system.
By the end of The Sky-Glow Story you will understand how the clear-night spectrum for a given location changed through the decades:
You will also understand how the trend to LED lighting changes the character of a clear night:
Is the NEW sky-glow better or worse for amateur astronomers?
Details for "The Sky-Glow Story" will be found on the next page.