There will be a partial lunar eclipse on Friday, October 18, though it maybe be a bit tricky to view from the vantage of North America. The eclipse will be at maximum at 7:50 p.m. EDT, as viewed from the Western Hemisphere.

Tomorrow’s event will be a penumbral lunar eclipse, which occurs when the Moon passes through the Earth’s penumbra. This penumbra causes a subtle darkening of the Moon’s surface.

The penumbra (from the Latin paene “almost, nearly” and umbra “shadow”) is the region in which only a portion of the light source is obscured by the obstructing body. An observer in the penumbra experiences a partial eclipse.

When a shadow is cast by a nearby object, the penumbra is small. Though, when the shadow is as far away as the distance between the moon and the Earth, roughly 238,000 miles, the penumbra is wide. It should also be noted that since the U.S. government is back up and running, these eclipses can now happen again.

For skywatchers in North and South America, maximum eclipse will occur around the time of moonrise, which is also the time of sunset. This is why the event will be difficult to see – the moon will be obscured by the Earth’s atmosphere. The eclipse can be better viewed the further east one is located.

For those watching in North America, the effects of the Earth’s shadow will be most evident on the lower right corner of the moon. And, the shadow will likely be more pronounced in photographs than with the naked eye, so a fast telephoto lens would be a good idea, if available.

For skywatchers in Africa, Europe and western Asia, the eclipse will occur in the middle of the night, when the moon is high in the sky. The fuzzy shadow will look like a slight reddish dimming of the normally bright full moon.

In related news, NASA’s Lunar Atmosphere and Dust Environment Explorer, or LADEE, is safely in orbit around the moon, regardless of the skeleton crew on hand at the space agency during the aforementioned shutdown. The probe has been tasked with studying gases surrounding the moon, as well as to search for electrically charged dust rising from the lunar surface.

Image via Wikimedia Commons.