This year, October's most spectacular show probably will be an old friend: the full hunter's moon.
When that moon rises on Oct. 18, it will be about as round as a rising moon ever gets. In the Twin Cities, for example, moonrise occurs at 6:12 p.m., just 26 minutes before it is at its fullest. As it rises, the moon passes through Earth's light outer shadow, or penumbra, but this eclipse will be barely noticeable at best.
The morning sky gives early birds a clear view of Jupiter and Mars in the east. Jupiter, a bright yellowish beacon, floats along in Gemini, ornamenting the knot of bright winter constellations on their journey from the morning sky to the evening sky.
Mars, lower and dimmer than Jupiter, begins the month just west of the Sickle -- stars that outline the head of Leo. The Red Planet glides past bright Regulus, at the base of the Sickle, and ends October below -- in this case, west of -- Leo's belly. Try going out about an hour before sunrise on about Oct. 14-16, when Mars and Regulus will be closest, or Oct 29-30, when a crescent moon visits the pair.
In the evening sky, Venus holds steady above the southwestern horizon while Saturn, in the west-southwest, heads toward the sun's afterglow. Look on Oct. 7 to see a waxing crescent moon between the two planets.
When night falls, the autumn constellations come out.
High in the south sails the Great Square of Pegasus, the mythical winged horse. Use binoculars to find a faint oval smudge halfway between the Square's northeast corner and W-shaped Cassiopeia; this is the Andromeda galaxy, the closest large neighbor to our Milky Way.
Lower in the sky, look for several "water" constellations.
Right below the Great Square, the Circlet of Pisces is fun to find. Southwest of the Circlet, the Y-shaped Water Jar is the focal point of Aquarius. Known as the water bearer, he is Ganymede, a handsome youth whom Zeus (Jupiter) made cup bearer to the gods. Appropriately, Ganymede also is one of Jupiter's four Galilean moons.
Southwest of Aquarius is chevron-shaped Capricornus, the sea goat. And the lone star far to the south is Fomalhaut, brightest in Piscis Austrinus, the southern fish.
The astronomy world has eagerly awaited the arrival of Comet ISON, which now is bearing down on the inner solar system in what appears to be its maiden -- and only -- voyage to our neighborhood. But it probably won't be the spectacle it once was hoped to be.
ISON is speeding in from the farthest reach of the solar system, a home for comets called the Oort Cloud. On Oct. 1, it sails above Mars in the eastern predawn sky, an event that will, if we're lucky, be imaged by the Mars rover Curiosity. As it hurtles down toward the sun -- still in the morning sky -- it will brighten, but it also will be harder to see. Only time will tell if ISON goes down in history as a dazzler or a disappointment. An animation of its orbit is on the NASA website at http://stereossc.nascom.nasa.gov/comet_ison.
There will be no moon lighting the way for trick-or-treaters this year as they re-enact rituals begun by ancient Celts to mark the start of the dark half of the year at sundown on Oct. 31. At that moment, a gap opened between the living world and the netherworld, and evil spirits cooped up for six months rushed out to bedevil humankind until sunrise May 1. All mortals could do was to try to ward them off with lanterns carved from gourds or with bribes of food. Back then, evil spirits were held responsible for all kinds of sickness, death and other misfortunes of winter -- a little more serious risk than having your windows soaped.
The University of Minnesota offers public viewings of the night sky at its Duluth campus in the Marshall W. Alworth Planetarium. Learn more at www.d.umn.edu/ planet.