In search of natural darkness

(Photo by Dion Ogust)

The surest known cause of breast cancer is the absence of nocturnal darkness. Studies have confirmed that women who work the night shift and therefore sleep when daylight is streaming into their bedroom, or those in cities who have streetlights leaking in and keeping their rooms from being fully dark, suffer altered melatonin levels that unfortunately correlate with a much higher breast cancer incidence.

In our 21st century, more than half the world’s population lives in an urban environment, with natural nocturnal darkness a phenomenon many only read about. But we who live in a rural setting still mostly enjoy the natural night and its splendors.

Still, there’s dark and then there’s really dark. Backyard astronomers seek out the latter because all sorts of gorgeous phenomena only materialize when there is no artificial skyglow.  I’m quite sure of this because, for the past 20 years, I’ve led annual tours to central Alaska for the Northern Lights, and to the Atacama Desert and the Andes Mountains to see Southern Hemisphere celestial wonders at their very best. Plus, I’ve observed the heavens from Death Valley, the Sonoran Desert, the Australian Outback, the Thar Desert and other places where the Milky Way blazes with such brilliance and that it actually casts shadows.


Our Catskill skies are not that good, although there are places that come close. Our very darkest region accessible by automobile (according to satellite-based maps and actual measurements) merely requires driving north or west on Route 28 just past Margaretville, then turning left on Route 30, and then parking in the pulloff just before the bridge over the Pepacton Reservoir. From that spot, using special sky-measuring equipment (an SQM meter), I’ve confirmed that the best Catskill skies attain a darkness level of 21.0 magnitude per square arcsecond, which is nicely unspoiled.

From such skies, the Milky Way displays countless dark superimposed nebulae that form intricate patterns that Central and South American cultures regarded as the central focal points of life itself. Still, the issue of darkness is often rife with confusion.

Before last week’s total eclipse in Chile, for example, newbies expected that a major attraction of the event would be seeing “darkness at noon.” They learned that it doesn’t get very dark during a total solar eclipse. (You can always read by the light cast by the solar corona.) During totality, your surroundings are still bathed in about the same brightness as on the night of a Full Moon – not to mention that darkness per se is never the objective or the draw. If you merely want darkness, just step into a closet or don’t pay your electric bill. Obviously, whether it’s detail within the Milky Way or the intricate patterns of the Aurora Borealis, we want dark skies because we can then observe astonishing phenomena that are otherwise hidden by light pollution.

A sky crammed with stars is one of those benefits. From the downtown area of a major city, one can see four to eight stars in the whole sky. From typical suburbs – say, around the Nassau/Suffolk line – around 100 stars appear. In my experience, the feeling of grandeur and infinitude that one can feel under the night sky requires at least 400 stars in the field of view.  For comparison, during the next ten days – when the Moon will be increasingly absent – our Ulster County firmament typically displays 1,600 stars at a time for those outside the sky glow from places like Kingston or New Paltz, which means the cutoff is magnitude 5. In case you wondered, truly pure skies display 2,500 to 3,000 stars at a sitting: a magnitude 6 limit. That’s what you see deep in the Catskills, like from the Pepacton Reservoir.

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