Mercury - is in line with the Sun on the 17th and so is lost in the glare until January, when it will emerge into the evening twlight.

Venus - rises just prior to 4:00 a.m. on December 1. The first magnitude star Spica, Venus, and the Moon form a triangle in Virgo on the morning of December 5. Venus enters Libra on December 12. It lies between Alpha and Beta Librae on December 19. Venus shrinks in apparent size from 18 to 15" while its disk waxes in illumination from 66 to 76%. Venus will be magnitude -4.2. Through a telescope, the planet will appear gibbous.

Mars - is very well placed for northern-hemisphere observers during December. It's positioned within 20 degrees of the zenith, as far north as it ever gets, every night for a minimum of two hours. Mars is less than half a degree north of the third magnitude star Epsilon Geminorum and shines with a brilliance of magnitude -1.4 on the night of December 3. The Martian northern-hemisphere vernal equinox takes place on December 9. Due to its highly elliptical orbit, the Red Planet is closest to the Earth on December 18. Mars is less than three degrees north of the bright open cluster M35 in Gemini from December 21 to December 28. On the night of December 23, it's just 2.5 degrees north of M35. Mars reaches opposition on the night of December 24 and thus rises at sunset, transits the meridian at midnight, and sets at sunrise. On the night of opposition, Mars has a declination of 26 degrees and 46 arc minutes and at midnight is thus almost 77 degrees above the southern horizon. Since the Martian day, or sol, is 37.4 minutes longer than a terrestrial one, Martian surface features appear to move 9.11 degrees to the west each day. Mare Sirenum is visible at the beginning of the month at midnight, followed by Solis Lacus (the Eye of Mars) and Sinus Meridiani at mid-month, and Syrtis Major when the planet reaches opposition. Mars travels eleven degrees westward during December but retrogrades back into the constellation of Taurus on December 30. The maximum diameter of 16" occurs on December 18th, when Mars is closest to the Earth. This is large enough to see the major surface features in a 3" telescope. The dust storms that occurred during July have subsided enough that the surface of the planet is becoming visible again. Besides the usual dark surface markings, the North Polar Hood should still be visible. See the Mars Profiler at http://www.skyandtelescope.com/observing/objects/javascript/mars for a hemispherical map of Martian surface features and http://www.skyandtelescope.com/observing/objects/javascript/mars_moons/index.html for the positions of the faint Martian moons Phobos and Deimos.

Jupiter - enters Sagittarius on December 2. It slips out of view by the second week of the month as it heads toward conjunction on December 23.

For detailed postions of Jupiter's Moons try this interactive javascript utility.

Saturn - rises shortly before midnight on December 1, at approximately 10:30 p.m. EST at midmonth, and at approximately 8:00 p.m. EST by month's end. It is at quadrature on December 1. Saturn's ring tilt angle is now only seven degrees. Titan (magnitude 8.5) is due north of the planet on December 4 and December 20. It is due south of Saturn on December 12 and December 28. Saturn's curious two-faced satellite Iapetus is due west of the planet by the listed separations on the following dates: December 2 (24"), December 8 (34"), December 14 (36"), December 20 (30"), December 26 (17"), and December 30 (6").

The Cassini spacecraft continues its observation of Saturn and its many moons and rings. For the latest images from Cassini, see:

http://saturn.jpl.nasa.gov/home/index.cfm

For detailed postions of Saturn's Moons try this interactive javascript utility.

Uranus - is located just east of 81 and 82 Aquarii. By the end of December, the planet's eastward progress takes it to within two degees of the fourth magnitude star Phi Aquarii. Look for it 42 degrees up in the south around 6 pm EST at mid-month. Uranus will be magnitude 5.9 and can be glimpsed with the naked eye from a dark site. Through a telescope, the planet will have a tiny 3.5 arc-second pale green disc.

A finder chart for Uranus can be found Here.

Neptune - located in Capricornus. Look for it 30 degrees up in the SSW around 6 pm EST at mid-month. At magnitude 7.9, Neptune can be seen with binoculars but a telescope is needed to see its 2.2" pale blue disc.

A finder chart for Neptune can be found Here.

Pluto - is in conjunction with the Sun on December 18, it is not visible this month.

Eris (pronounced "EE-ris") - formerly known as Xena, 2003 UB313, and "the tenth planet" - is magnitude 19 in central Cetus, high in the south during evening.

For detailed information please visit Astronomical Delights

Comet 17P/Holmes - continues to expand to momumental proportions as the comet travels through western Perseus. The historic comet will pass approximately 1.5 degrees to the northwest of the open cluster NGC 1245 on the night of December 2 and a bit more than 2 degrees to the west of the cluster on December 13.

The Geminid Meteor Shower - peaks on the night of December 13-14. About 30-60 Geminids can be seen every hour radiating from an area near Castor. The waxing crescent Moon sets around 9 pm and will not interfere with meteor watching. The best times to watch are from 8 pm till dawn. Face east or south for the best view.