A total penumbral lunar eclipse is a

lunar eclipse A lunar eclipse occurs when the Moon moves into the Earth's shadow. Such alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Earth ...

that occurs when the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

becomes completely immersed in the penumbral cone of the Earth without touching the

umbra The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast. Th ...

. The path for the Moon to pass within the penumbra and outside the umbra is very narrow. It can only happen on the Earth's northern or southern penumbral edges. In addition, the size of the penumbra is sometimes too small where the Moon enters it to contain the Moon. The width of the Earth's penumbra is determined by the Sun's

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...

at the time of the eclipse, and the Moon's angular diameter is larger than the Sun over part of its

elliptical orbit In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. In a stricter sense, it ...

, depending on whether the eclipse occurs at the nearest (

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

) or farthest point (

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

) in its orbit around the Earth. The majority of the time, the size of the Moon and the size of the Earth's penumbra where the Moon crosses it mean that most eclipses will not be total penumbral in nature.

Frequency

Total penumbral eclipses constitute a relatively small fraction of lunar eclipses, and the distribution of these events is uneven, occurring between 0 and 9 times per century. The period of this variation is approximately 600 years and also correlates with the frequency of total umbral eclipses and tetrads. The maximum number in Fred's 5K canonTotal penumbral lunar eclipses are indicated by the ''Nx'' eclipse type in

Fred Espenak Fred Espenak is a retired emeritus American astrophysicist. He worked at the Goddard Space Flight Center. He is best known for his work on eclipse predictions. He became interested in astronomy when he was 7–8 years old, and had his first tel ...

'
Lunar Eclipse canon
is eight for saros 19. Saros 32 and 132 have seven. Saros 58, 95, and 114 have six. Saros 114 is the only saros in the canon to have a total of seven total penumbral lunar eclipses that are not all in a row. Likewise, saros 169 has five total penumbral eclipses, but only four of them occur consecutively.

Saros series with multiple consecutive total penumbral eclipses

This table summarizes which

saros series The saros () is a period of exactly 223 synodic months, approximately 6585.3211 days, or 18 years, 10, 11, or 12 days (depending on the number of leap years), and 8 hours, that can be used to predict eclipses of the Sun and Moon. One saros period a ...

contain four or more consecutive total penumbral eclipses.

Summary frequency of total penumbral, total umbral and tetrad events 501–2500

Total penumbral eclipse frequency by century

List of total penumbral lunar eclipse events 1901–2200

Notes

References