Unlike during a total lunar eclipse when the sun, Earth and moon are in almost perfect alignment, penumbral eclipses occur when the three bodies are only imperfectly aligned during the full moon phase. At these times, the Earth only blocks some of the suns light from directly falling on the moon's surface.

Is a penumbral eclipse a lunar eclipse?

A total penumbral lunar eclipse is a lunar eclipse that occurs when the Moon becomes completely immersed in the penumbral cone of the Earth without touching the umbra. The path for the Moon to pass within the penumbra and outside the umbra is very narrow.

How does a penumbral lunar eclipse appear in the sky?

A penumbral eclipse

Like other lunar eclipses, penumbral eclipses occur whenever the Earth passes between the Moon and Sun, such that it obscures the Sun's light and casts a shadow onto the Moon's surface. But unlike other kinds of eclipses, they are extremely subtle events to observe.