A "Blood Moon" is a total lunar eclipse, which occurs when the earth passes between the sun and the moon such that it blocks direct sunlight from reaching the lunar surface.  This can only occur when the moon is full as that is when the moon is directly opposite the sun relative to the earth.  It does not happen every full moon because the moon is usually either above or below the earth's shadow.  Only when the moon and earth are in alignment with the sun vertically, so to speak, as well as horizontally, does an eclipse take place. This one is the last of a "tetrad" of lunar eclipses occuring over the last two years. What is exciting is this one will be visible here in central Arkansas as a total eclipse, makeing it a "blood moon".

The eclipse proper will begin at approximately 8:07 PM at which time a darkening of the moon at the edge will begin.  As this progresses it will start to look like Pac Man is taking a growing bite out of the lunar disc, until totality is reached at approximately 9:47 PM.  At this point the moon will be a dark red, as no direct sun light will be reaching the moon, only what is refracted through earth's atmosphere.  The night sky will be almost as dark as a moonless night, making deep sky observing possible during totality.  Totality will not end until 11:27 PM.  For more on lunar eclipses go here:

 
http://www.mreclipse.com/Special/LEprimer.html

You can view this event from just about anywhere with a clear sky and no instrument is necessary though binoculars or a small scope can add to the experience.  CAAS is opening its observing site to the public for this event starting at 7:00 PM.  Once totality is reached we can take advantage of the remote location to observe deep sky objects.  Be advised that it is about a fourty minute drive from I430/Hyw.10 interchange to the observatory.  Unlike most club sponsored events, events on our observing site require pre-registration.  See the Society's website for details on registering:  caas@caasastro.org