Why Sunday's penumbral lunar eclipse is not worth staying up for

The Moon will pass through the Earth's shadow, but not the good part.

Every shadow has two parts, the darker umbra at the center surrounded by a larger, but not nearly as dark penumbra. While partial and total lunar eclipses produce a noticeable darkening of the Moon as it passes through Earth's umbra, penumbral lunar eclipses like tonight's are much more subtle.

If you look closely, you might notice the Moon grow a bit darker beginning at 12:53 a.m. EDT. By 3:18 a.m. all but about 10% of the face of the Moon will be within the Earth's penumbral shadow, which is about 500 times brighter than the umbral shadow. The effect isn't much different than a thin cloud passing in front of the Moon.

On the bright side, even an unimpressive lunar eclipse does signal a more interesting solar one.

Lunar and solar eclipses come in pairs, separated by two weeks. The partial lunar eclipse on August 7, 2017 was followed by the total solar eclipse that passed through the Carolinas on August 21, 2017. Tonight's penumbral lunar eclipse will be followed by a total solar eclipse stretching from Texas to Maine..

This happens twice yearly as the Moon's orbit and it's 5º tilt, aligns with the Earth's orbit around the Sun.  That alignment occurs once when the Moon is between the Earth and Sun (solar eclipse), and once when the Moon is on the other side of the Earth (lunar eclipse).