Solar eclipse of May 20, 1966

An annular solar eclipse occurred at the Moon's ascending node of orbit on Friday, May 20, 1966, with a magnitude of 0.9991. 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. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible from Guinea (including the capital city Conakry), Mali, Algeria, Libya, Greece, Turkey, the Soviet Union (today's Russia and Kazakhstan) and China. The Sun's altitude was 70°.

Observations
During this eclipse, the apex of the moon's umbral cone was very close to the Earth's surface, and the magnitude was very large. The edges of the moon and the sun were very close to each other as seen from the Earth. Baily's beads on the lunar limb, which are usually only visible during a total solar eclipse, could also be seen. Therefore this eclipse was also an excellent opportunity to measure the size and shape of the Earth, as well as the mountains and valleys on the lunar limb. Many scientists observed the annular eclipse in Greece and Turkey, which are close to the location of maximum eclipse and have better observation conditions. The observation sites in Greece were mainly concentrated in Saronida and Anavyssos south of Athens, while those in Turkey were mainly concentrated in Ayvalik, across the sea facing the Greek island Lesbos.

Similar to the Baily's beads, the corona is generally only visible in a total solar eclipse. Because the magnitude of this annular eclipse was close to 1, some predicted that the corona would be visible. An observation team went to Lesbos Island but only saw the Baily's beads, not the corona.

Prior to it, the two hybrid solar eclipses of April 17, 1912 and April 28, 1930, and another annular solar eclipse of May 9, 1948 also belonging to Solar Saros 137, also occurred with a magnitude close to 1. Observations were made near Paris in France, Camptonville, California and Rebun Island in Japan respectively.

Eclipses in 1966

 * A penumbral lunar eclipse on May 4, 1966.
 * An annular solar eclipse on May 20, 1966.
 * A penumbral lunar eclipse on October 29, 1966.
 * A total solar eclipse on November 12, 1966.

Metonic

 * Preceded by: Solar eclipse of July 31, 1962
 * Followed by: Solar eclipse of March 7, 1970

Tzolkinex

 * Preceded by: Solar eclipse of April 8, 1959
 * Followed by: Solar eclipse of June 30, 1973

Half-Saros

 * Preceded by: Lunar eclipse of May 13, 1957
 * Followed by: Lunar eclipse of May 25, 1975

Tritos

 * Preceded by: Solar eclipse of June 20, 1955
 * Followed by: Solar eclipse of April 18, 1977

Solar Saros 137

 * Preceded by: Solar eclipse of May 9, 1948
 * Followed by: Solar eclipse of May 30, 1984

Inex

 * Preceded by: Solar eclipse of June 8, 1937
 * Followed by: Solar eclipse of April 29, 1995

Triad

 * Preceded by: Solar eclipse of July 19, 1879
 * Followed by: Solar eclipse of March 20, 2053