An annular

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...

occurred at the Moon's

ascending node An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit, which is contained in the reference plane, has no nodes. Planes of reference Common planes of referenc ...

of orbit on Friday, May 20, 1966, with a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of 0.9991. A

occurs when the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

passes between

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, 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 The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the '' visual ...

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. The Moon's apparent diameter was near the average diameter because it occurred 6.8 days after

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

(on May 13, 1966, at 14:00 UTC) and 7.2 days before

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

(on May 27, 1966, at 15:00 UTC). Annularity was visible from

Guinea Guinea, officially the Republic of Guinea, is a coastal country in West Africa. It borders the Atlantic Ocean to the west, Guinea-Bissau to the northwest, Senegal to the north, Mali to the northeast, Côte d'Ivoire to the southeast, and Sier ...

(including the capital city

Conakry Conakry ( , ; ; ; ) is the Capital city, capital and largest city of Guinea. A port city, it serves as the economic, financial and cultural centre of Guinea. Its population as of the 2014 Guinea census was 1,660,973. The current population of C ...

Mali Mali, officially the Republic of Mali, is a landlocked country in West Africa. It is the List of African countries by area, eighth-largest country in Africa, with an area of over . The country is bordered to the north by Algeria, to the east b ...

Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...

Libya Libya, officially the State of Libya, is a country in the Maghreb region of North Africa. It borders the Mediterranean Sea to the north, Egypt to Egypt–Libya border, the east, Sudan to Libya–Sudan border, the southeast, Chad to Chad–L ...

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

, the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

(today's

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

and

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...

) and

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. A partial eclipse was visible for parts of

North Africa North Africa (sometimes Northern Africa) is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region. However, it is sometimes defined as stretching from the Atlantic shores of t ...

Central Africa Central Africa (French language, French: ''Afrique centrale''; Spanish language, Spanish: ''África central''; Portuguese language, Portuguese: ''África Central'') is a subregion of the African continent comprising various countries accordin ...

Northeast Africa Northeast Africa, or Northeastern Africa, or Northern East Africa as it was known in the past, encompasses the countries of Africa situated in and around the Red Sea. The region is intermediate between North Africa and East Africa, and encompasses ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

West Asia West Asia (also called Western Asia or Southwest Asia) is the westernmost region of Asia. As defined by most academics, UN bodies and other institutions, the subregion consists of Anatolia, the Arabian Peninsula, Iran, Mesopotamia, the Armenian ...

Central Asia Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Pers ...

North Asia North Asia or Northern Asia () is the northern region of Asia, which is defined in geography, geographical terms and consists of three federal districts of Russia: Ural Federal District, Ural, Siberian Federal District, Siberian, and the Far E ...

, and

South Asia South Asia is the southern Subregion#Asia, subregion of Asia that is defined in both geographical and Ethnicity, ethnic-Culture, cultural terms. South Asia, with a population of 2.04 billion, contains a quarter (25%) of the world's populatio ...

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 The Baily's beads, diamond ring or more rarely double diamond ring effects, are features of total and annular solar eclipses. Although caused by the same phenomenon, they are distinct events during these types of solar eclipses. As the Moon cover ...

on the

lunar limb The lunar limb is the edge of the visible surface (disc) of the Moon as viewed from Earth. Seen from afar, it looks like a circular arc, but with higher resolution, it can be seen that the Moon’s surface is not flat and therefore its profile is ...

, 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 Anavyssos () is a town and a former municipality in East Attica, Greece located in the Athens Riviera. Since the 2011 local government reform it is part of the municipality Saronikos, of which it is a municipal unit. The municipal unit has an are ...

south of

Athens Athens ( ) is the Capital city, capital and List of cities and towns in Greece, largest city of Greece. A significant coastal urban area in the Mediterranean, Athens is also the capital of the Attica (region), Attica region and is the southe ...

, while those in Turkey were mainly concentrated in Ayvalik, across the sea facing the Greek island

Lesbos Lesbos or Lesvos ( ) is a Greek island located in the northeastern Aegean Sea. It has an area of , with approximately of coastline, making it the third largest island in Greece and the List of islands in the Mediterranean#By area, eighth largest ...

. Similar to the Baily's beads, the

corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus or disease responsible for the COVID-19 ...

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 An annular solar eclipse occurred at the Moon's ascending node of orbit between Saturday, May 8 and Sunday, May 9, 1948, with a magnitude of 0.9999. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly o ...

also belonging to Solar Saros 137, also occurred with a magnitude close to 1. Observations were made near

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

, Camptonville, California and

Rebun Island is an island in the Sea of Japan off the northwestern tip of Hokkaidō, Japan. The island sits off the coast of Hokkaidō. Rebun stretches from north to south and from east to west. The island covers approximately . Rebun Island is located ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

respectively.

Eclipse details

Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.

Eclipse season

This eclipse is part of an

eclipse season An eclipse season is a period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Orbit of the Moon, Moon's orbital plane (orbital inclination, tilted five degrees to the ecliptic, Earth ...

, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a

fortnight A fortnight is a unit of time equal to 14 days (two weeks). The word derives from the Old English term , meaning "" (or "fourteen days", since the Anglo-Saxons counted by nights). Astronomy and tides In astronomy, a ''lunar fortnight'' is hal ...

Related eclipses

Eclipses in 1966

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

Metonic

* Preceded by:

Solar eclipse of July 31, 1962 Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

* Followed by: Solar eclipse of March 7, 1970

Tzolkinex

* Preceded by:

Solar eclipse of April 8, 1959 An annular solar eclipse occurred at the Moon's descending node of orbit on Wednesday, April 8, 1959, with a magnitude of 0.9401. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image ...

* Followed by:

Solar eclipse of June 30, 1973 A total solar eclipse occurred at the Moon's descending node of orbit on Saturday, June 30, 1973, with a magnitude of 1.0792. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of t ...

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 A total solar eclipse occurred at the Moon's descending node of orbit on Monday, June 20, 1955, with a magnitude of 1.0776. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of ...

* Followed by: Solar eclipse of April 18, 1977

Solar Saros 137

* Preceded by:

Solar eclipse of May 9, 1948 An annular solar eclipse occurred at the Moon's ascending node of orbit between Saturday, May 8 and Sunday, May 9, 1948, with a magnitude of 0.9999. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly o ...

* 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 An annular solar eclipse will occur at the Moon's descending node of orbit on Thursday, March 20, 2053, with a magnitude of 0.9919. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the imag ...

Solar eclipses of 1964–1967

Saros 137

Metonic series

Tritos series

Inex series

Notes

References

{{Solar eclipses 1966 5 20 1966 in science 1966 05 20 May 1966