Solar eclipse of June 8, 1918

A total solar eclipse occurred at the Moon's descending node of orbit on Saturday, June 8, 1918, with a magnitude of 1.0292. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. The eclipse was viewable across the entire contiguous United States, an event which would not occur again until the solar eclipse of August 21, 2017.

The Path
The path of totality started south of Japan, went across the Pacific Ocean, passing northern part of Kitadaitō, Okinawa and the whole Tori-shima in Izu Islands on June 9 (Sunday), and then acrossed the contiguous United States and British Bahamas (today's Bahamas) on June 8 (Saturday). The largest city to see totality was Denver, although many could theoretically see it as the size of the shadow was between 70 and 44 mi across as it traveled across America. The longest duration of totality was in the Pacific at a point south of Alaska. The path of the eclipse finished near Bermuda.

Besides the path where a total solar eclipse was visible, a partial solar eclipse was visible in the eastern part of East Asia, northern part of Northern Europe, eastern part of Micronesia, Hawaii Islands, northeastern Russian Empire, the entire North America except the Lesser Antilles, and the northwestern tip of South America.



U.S. Observation team
The path of the eclipse clipped Washington state, and then moved across the whole of Oregon through the rest of the country, exiting over Florida. The U.S. Naval Observatory (USNO) obtained a special grant of $3,500 from Congress for a team to observe the eclipse in Baker City, Oregon. The team had been making preparations since the year before, and John C. Hammond led the first members to Baker City on April 11. The location was important, as it influenced the probability of cloud cover and the duration and angle of the sun during the eclipse. The team included Samuel Alfred Mitchell as its expert on eclipses, and Howard Russell Butler, an artist and physicist. In a time before reliable colour photography, Butler's role was to paint the eclipse at totality after observing it for 112.1 seconds. He noted later that he used a system of taking notes of the colours using skills he had learned for transient effects.

Joel Stebbins and Jakob Kunz from the University of Illinois Observatory made the first photoelectric photometric observations of the solar corona from their observing site near Rock Springs, Wyoming

Observation
As the total eclipse approached, the team watched as clouds obscured the Sun. The clouds did clear, but during their most important observations the Sun was covered by a thin cloud; the Sun was completely visible five minutes later. This was not unusual, as cloudy conditions were reported across the country, where the eclipse was also observed from the Yerkes Observatory, Lick Observatory, and Mount Wilson Observatory.

Following the 1915 prediction of Albert Einstein's General theory of relativity that light would be deflected when passing near a massive object such as the Sun, the USNO expedition attempted to validate Einstein's prediction by measuring the position of stars near the Sun. The cloud cover during totality obscured observations of stars, though, preventing this test of the validity of general relativity from being completed until the solar eclipse of May 29, 1919.

Eclipses in 1918

 * A total solar eclipse on June 8, 1918.
 * A partial lunar eclipse on June 24, 1918.
 * An annular solar eclipse on December 3, 1918.
 * A penumbral lunar eclipse on December 17, 1918.

Metonic

 * Preceded by: Solar eclipse of August 21, 1914
 * Followed by: Solar eclipse of March 28, 1922

Tzolkinex

 * Preceded by: Solar eclipse of April 28, 1911
 * Followed by: Solar eclipse of July 20, 1925

Half-Saros

 * Preceded by: Lunar eclipse of June 4, 1909
 * Followed by: Lunar eclipse of June 15, 1927

Tritos

 * Preceded by: Solar eclipse of July 10, 1907
 * Followed by: Solar eclipse of May 9, 1929

Solar Saros 126

 * Preceded by: Solar eclipse of May 28, 1900
 * Followed by: Solar eclipse of June 19, 1936

Inex

 * Preceded by: Solar eclipse of June 28, 1889
 * Followed by: Solar eclipse of May 20, 1947

Triad

 * Preceded by: Solar eclipse of August 7, 1831
 * Followed by: Solar eclipse of April 8, 2005

Other links

 * NASA graphic
 * Eclipse of June 8, 1918. Contact print from the original glass plate negative. Lick Observatory Plate Archive, Mt. Hamilton.
 * Foto and sketch of Solar Corona June 8, 1918