An annular solar eclipse occurred at the Moon's ascending node of orbit on Friday, May 20, 1966,[1] with a magnitude of 0.9991.

[2] 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.

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.

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.

[3] Similar to the Baily's beads, the corona is generally only visible in a total solar eclipse.

Observations were made near Paris in France, Camptonville, California and Rebun Island in Japan respectively.

[7] The metonic series repeats eclipses every 19 years (6939.69 days), lasting about 5 cycles.

Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee).