Wednesday, August 3, 2016

Lunar Eclipse - August 18, 2016

You may soon hear, if you haven't already, about an upcoming lunar eclipse view-able from the United States.  There is indeed a lunar eclipse of sorts taking place on August 18, 2016 and it is view-able from the United States, but it all depends on your definition of view-able.  Consider the image below.

A lunar eclipse occurs whenever Earth is positioned directly between the Sun and the Moon.  As a result, the Earth casts a shadow onto the surface of the Moon that we can view from Earth.  A total lunar eclipse occurs when the Moon is in the darkest part of the shadow shown above.  If the Moon is in the lighter part of the shadow above there is still an eclipse, called a penumbral eclipse.  The Moon will darken a bit in the sky, but it is not nearly as impressive as a total eclipse.  Even that's not happening later this month.  On August 18, the Moon will be near the penumbra shadow line, but not fully within.  This it is close to an eclipse, but not actually a true eclipse.  If you have detailed observing equipment, you may detect a slight drop in the Moon's brightness, but this is nothing you'd notice with your naked eye.  

In other words, don't get excited.  The next total lunar eclipse view-able from the United States will take place on January 20, 2019.  Be patient.  :-)

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