Umbra vs penumbra full#

This is because the plane in which the moon orbits Earth is not the same as the plane in which Earth orbits the Sun ( called the ecliptic).

Umbra vs penumbra full#

But, lunar eclipses do not occur at every full moon (and, analogously, solar eclipses do not occur at every new moon). At every full moon, Earth is essentially between the Sun and the moon. Now, regarding the moon's orbit and the Sun/moon/Earth arrangement. Thus, while penumbral lunar eclipses are still eclipses, the shadowing is so subtle that they can be difficult to see and photograph. These eclipses are called total and partial lunar eclipses (depending on how much of the moon passes through the umbra.) Eclipses where the moon passes through Earth's penumbra (accordingly designated 'penumbral lunar eclipses' ) produce only a slight darkening of the moon. Lunar eclipses involving the umbra are readily apparent because the moon becomes nearly invisible.

In Earth/moon lunar eclipses, only the umbra and penumbra are important because the antumbra begins outside of the moon's orbit. The antumbra occurs at large distances from Earth. The antumbra is another lighter shadow which occurs where Earth appears smaller than the Sun so that the edges of the Sun can be seen as a ring around Earth. The penumbra is the lighter outer part of the shadow where only a portion of the Sun is covered. The umbra is the darkest part of the shadow and is where all light from the Sun is blocked by Earth. There are three 'types' of shadow cast by Earth called the umbra, penumbra, and antumbra.

This graphic gives a decent summary, with more discussion below.įirst, regarding shadows. One concerns the shadow(s) and the other concerns the orbit of the moon around Earth.

There are (at least) two reasons that a lunar eclipse cannot be photographed every time the Earth is between the Sun and the moon. Why can you only photograph a lunar eclipse sometimes when the earth is between the sun & moon?Ī lunar eclipse is when Earth prevents sunlight from reaching the moon (i.e., when the moon passes through Earth's shadow).