Sky & Telescope - October 2023 - 36

Eclipse Preview
Northern limit of annularity
Path of Annularity
Southern limit of annularity
85%
80%
75%
memorable total eclipse came ashore. At Oregon Dunes
National Recreational Area the Sun stands 17° above the
eastern horizon and annularity lasts 4m 34s. Unfortunately,
the weather along the coast this October is forecast to be
much less friendly than it was in August 2017. Twenty years
of satellite observations show that October cloud amounts
average 60% to 70% along the Oregon coast, and this holds
as far inland as the Cascade Range. Cloudy skies are particularly
frequent in the Willamette Valley, a location that was a
crowd favorite in 2017.
Traveling with a supersonic velocity of 9,300 km/h (more
than seven times the speed of sound), the antumbra's path
is 221 km wide as the shadow races across Oregon. Eugene's
population of 175,000 makes it the third-largest city in the
state. Although it lies 62 km north of the central line, its
citizens can witness an annular phase lasting 3m 54s. This is
a consolation prize since Eugene was just outside the path of
totality in 2017.
Other Oregon cities in the path include Corvallis, Roseburg,
Coos Bay, Medford, and Klamath Falls. Crossing
the Cascade Range, the eclipse track includes Crater Lake
National Park, where the duration of annularity is 4m 32s.
Fortunately, cloud cover declines quickly along the eclipse
path. As the graph presented on page 39 shows, average
cloudiness drops by about 20% from what it was at the start
of the eclipse, into the mid-40% range, as the shadow crosses
36 OCTOBER 2023 * SKY & TELESCOPE
ANTUMBRAL ALLEY The annular eclipse path traverses nine American
states from Oregon to Texas, where the Moon's antumbral shadow
leaves the U.S. and passes over the Gulf of Mexico before making landfall
once again in Mexico's Yucatán Peninsula. The percentage lines refer to
eclipse obscuration, which is the fraction of the Sun's area covered by the
Moon. Only locations within the eclipse path (colored green) will witness
annularity. (Map courtesty of Michael Zeiler, GreatAmericanEclipse.com.)
from Crater Lake to the Nevada-California border. However,
the central line may not be the best place to be. Cloud cover
varies across the width of the track, and the most promising
conditions lie on the south side, particularly near Klamath
Falls and Chiloquin.
The Moon's shadow next enters northeastern California
and northern Nevada while barely clipping the southwestern
corner of Idaho. California's Lava Beds National Monument
(50 km south-southeast of Klamath Falls, Oregon) straddles
the path's southern limit, but locations along the Monument's
northern border still receive 1 minute of annularity.
Much of northern Nevada has a low population density.
Elko (population 21,000), the largest city in the path located
45 km north of the central line, will experience 4m 19s of
annularity, while Ely (population 4,000), in eastern Nevada,
will witness 3m 40s of ring of fire. Just before crossing the
Nevada-Utah state line at 9:26 PDT, the antumbra encounters
Great Basin National Park (60km southeast of Ely),
where annularity persists for 3m 55s.
Victoria
Olympia
Vancouver
Corvallis
Eugene
Coos Bay
Springfield
Roseburg
Medford
Klamath Falls
Eureka
Portland
Salem
Sacramento
San
Jose
Salt Lake City
Richfield
Parowan
Monticello
Flagstaff
Boise
Winnemucca
Elko
Reno
Ely
Fresno
Las
Vegas
Santa Barbara
http://www.GreatAmericanEclipse.com
Sky & Telescope - October 2023

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