On Friday night (February 10, 2017) here in Maine we will be able to see a penumbral lunar eclipse.
A lunar eclipse occur when the Moon passes through Earth’s shadow and the Sun’s light is blocked from reaching the Moon. Lunar eclipses have three flavors or – total, partial and penumbral – with the most dramatic being a total lunar eclipse, in which Earth’s shadow completely covers the moon. Lunar eclipses are only possible at Full Moon when the Sun, Earth and Moon are perfectly lined up. Due to the fact that the Moon’s orbit around Earth is in a slightly different plane than Earth’s orbit around the Sun, alignment for eclipses doesn’t occur at every Full Moon.
The Earth casts two shadows: The umbra is a full, dark shadow. The penumbra is a lighter outer shadow. During lunar eclipses, the Moon passes through either one, or in the case of a total lunar eclipse, both shadows. Lunar eclipses unfold over around two hours or so as the Moon passes through the shadows in stages.
The eclipse will physically start at 5:32 pm and finish at 9:55 pm, but in terms of visibility start looking to notice a change around 6:14 pm when you will start to notice darkening on the west (left) side of the Moon. The eclipse is at its maximum at 7:44 pm which is when it will be completely in Earth’s penumbral shadow. From there it will lighten up until 9:14 pm when you will no longer be able to perceive any darkening. For a nice diagram of the visibility and shadows see the NASA Eclipse website.
This eclipse is not a total lunar eclipse, so the Moon will not turn red or coppery colored, instead you will see a slight darkening of the Moon. It is worth taking a look at, so let’s keep our fingers crossed for clear weather Friday night!
The next opportunity to see a lunar eclipse in the United States is January 31, 2018. That one will be total for parts of the US, but here in Maine it will set before totality so you will need to travel west for a chance to see it.