18 Nebraskaland • October 2020
IN THE FIELD
My two favorite times of the day are dawn and dusk
— twilight — that space between day and night. The
sky is transformed in these hours: The landscape becomes
highlighted by changing colors, and we get to start anew.
Animals certainly respond to twilight as some become active
and others come in to roost or bed down.
What defines twilight is the angle of the sun below the
horizon when the sky is still illuminated, and there are three
defined categories. After the sun has dipped below your
horizon (sunset), civil twilight starts and is the brightest
category of twilight. The human eye can distinguish
landforms and terrestrial objects, though the sky is dark
enough that Venus can be seen — sometimes called the
morning or evening star. It is the perfect time to capture
those animals with your camera lens.
A few shades darker is nautical twilight, defined as such
when the sun is 6 to 12 degrees below your horizon. As the
name implies, it is the time when one can use the stars for
navigation and the horizon is distinguishable, assuming
clouds are not in your way.
When the sun is 12 to 18 degrees from your horizon,
astronomical twilight occurs. The dimmest stars can be
visible with the naked eye, though some may find it difficult
to distinguish this faintest of twilight from the dark of
night. How long do we have to capture twilight? About 90
to 120 minutes, varying a bit by time of year. We can thank
our atmosphere and all the particles and gasses therein for
these hours of dawn and dusk. They illuminate our sky by
scattering the light of someone else's day.
Martha D. Shulski, at the University of Nebraska-Lincoln, is
the director of the Nebraska State Climate office.
By Martha D. Shulski
BETWEEN DAY AND NIGHT
WIND
TURBINES
SPIN
AT
TWILIGHT
ON
THE
NEBRASKA
PUBLIC
POWER
DISTRICT'S
WIND
FARM
NEAR
AINSWORTH
PHOTO
BY
JENNY
NGUYEN-WHEATLEY
