In writing this essay, my intention was to be as thorough as possible and include a spectral analysis of sky-glow. My spectral discoveries 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".
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. These were often installed in a polluting manner. 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.
As we identify it today, light-pollution 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 (~1960 through ~1983), light-levels everywhere increased a minimum of 3x the former incandescent levels. Click for large pop-up..
Then came high-pressure-sodium (HPS) lighting. A dreadful period for astronomers because light-levels soared and the 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 for this code system.
By the end of The Sky-Glow Story you will understand why and 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? What are the criteria in making such a determination?
Details for "The Sky-Glow Story" will be found on the next page.
