A lunar eclipse is an event in astronomy that occurs when the Earth lies between the Sun and Moon, thus blocking the solar radiation and casting a shadow of the Earth into the Moon's surface. It occurs when the Sun, Earth, and Moon, are aligned in a straight line. This is the reason as to why it always falls on a full moon night, when the Sun and Moon are exactly opposite to each other.
In order to understand the types of lunar eclipses, let's first learn about the shadow of the Earth. There are two distinctive parts in the Earth's shadow, viz., the umbra and penumbra. The umbra is the darkest in which there is complete concealing of solar radiation; whereas, in the penumbra, there is partial blockage of solar radiation, resulting in subtle darkening. Depending upon the shadow of the Earth that falls on the Moon, astronomers categorized it into three different types, namely, penumbral, partial, and total.
This, as the name suggests, occurs when the Moon is positioned in the Earth's penumbra. It is hard to detect by an unaided eye; and is usually viewed with the help of a telescope. A total penumbral eclipse is a type when the Moon falls entirely within the penumbral shadow. It occurs rarely and the brightness of the Moon's surface differs from one portion to another; the area of the moon close to umbra is comparatively darker than the remaining portion. About 35 percent lunar eclipses are of penumbral type.
This occurs when a portion of the Moon passes the Earth's umbra. It is easily detectable by our naked eye. However, based on the portion of the Moon that passes through the umbra, at times it may be undetectable. In its final stages, the shadowed portion of the Moon turns reddish. About 30 percent lunar eclipses are of this type.
This occurs when the Moon lies exclusively in the Earth's umbra. During the event of total lunar eclipse, the Moon appears vibrant red in color. As per astronomical calculation in relation to the Moon's speed, it may last for about 107 minutes. It occurs when the Moon lies entirely within the umbral shadow; it usually lasts for about an hour. About 35 percent lunar eclipses are of this type.
It is to be noted that unlike a solar eclipse, a lunar eclipse is safe to view with our naked eyes. The Moon appears extraordinarily bright, before and after the event, due to the direct reflection of sunlight by the Moon's surface. On an average, there are two occurrences of this event, per year.