Saturday, July 16, 2016

Seeing spot(light)s


The dawn gave us Time
enough for our eyes to adjust
by dilation and securely
put away our Imagination.

Still, we can rely on the day
which washes out
lines in shadow,
and though
we act like we know
how it will go
down
in lumens and lux
by observing magnitudes
we are too tiny to see.

When the sun comes up,
let us pretend
it has never been
done before
this way
we can see
All
the stars
conceivably.



Photo credit: By NASA/JPL (http://photojournal.jpl.nasa.gov/jpeg/PIA00576.jpg) [Public domain], via Wikimedia Commons.
Detail via Wikimedia: A Martian sunrise was captured in this Viking 2 Lander picture taken June 14, 1978, at the spacecraft's Utopia Planitia landing site. The data composing this image were acquired just as the Sun peaked over the horizon on the Lander's 631st sol (Martian solar day). Pictures taken at dawn (or dusk) are quite dark except where the sky is brightened above the Sun's position. The glow in the sky results as light from the Sun is scattered and preferentially absorbed by tiny particles of dust and ice in the atmosphere. When the Viking cameras are calibrated for darker scenes, the "sky glow" tends to saturate their sensitivity and produce the bright regions seen here. The "banding" and color separation effects are also artifacts, rather than real features, and are introduced because the cameras are not able to record continuous gradations of light. The cameras must represent such gradations in steps (bands) of brightness and color, and the process sometimes produces some "false" colors within the bands. The scattering of light closest to the Sun's position tends to enhance blue wavelengths. The narrowing sky glow nearer the horizon above the Sun's position occurs as a result of light extinction. At that elevation, the optical path of sunlight through the atmosphere is at its longest penetration angle, and a substantial portion of the light is simply prevented from reaching the cameras by the dust, ice particles and other material in its way.

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