Arguably the millennium won't begin until Jan. 1, 2001, but much of the public believes it will start Jan. 1, 2000. At worst, we get two huge, world-wide parties out of this calendar quandary.

As this millennium winds down, the planets jump into the hoopla. They begin to line up now for an end-of-the year, all-night, all-planet pageant.

Right now Mars hangs in the constellation Libra and as September wears on, the red planet distances itself from Libra and makes its way toward the constellation Scorpius. During the middle of the month, Mars elbows its way near the bright red star Antares. With both objects being red and similarly bright, an unknowing eye could mistake one object for the other.

Don't fret: Antares will likely appear to flicker while Mars's reddish-orange tint remains steady. If you're facing south, Antares will be to the lower left of Mars. As the month wanes, Mars makes its way closer to Sagittarius.

Jupiter is ready to become a prime-time player. It now rises at about 10 p.m., and by the end of the month it gives us about two hours more of prime-time viewing, rising at about 8 p.m.

Find Jupiter in between the constellations Pisces and Aries right now. The large ball of gas crosses the meridian at about 4:30 a.m. Looking south, you'll see Jupiter on the left side of Pisces, appearing at a strong negative second magnitude. That's ample brightness for viewing through the late-summer, urban haze.

Between the constellations Pisces and Taurus, Saturn rises in the east about 45 minutes after Jupiter makes its own grand entrance. This zero magnitude planet, still bright enough to see from the city, crosses the meridian now just before sunrise, then earlier as September wears on.

Venus lords over the morning, providing spectacular views. At about 5 a.m., it ascends the eastern heavens at a negative fourth magnitude. It's hard to miss.

The autumnal equinox occurs Sept. 23 at 7:31 a.m. EDT (11:31 a.m. Universal Time). That is the astronomical moment when the sun appears to cross the equator into the Southern Hemisphere, according to the U.S. Naval Observatory.

Down-to-Earth Events

Sept. 5 -- Astronomer Lee Mundy discusses "The Dusty Origin of Stars" at the University of Maryland astronomy department's open house. Following the lecture, gaze at the sky through the telescope at the university's observatory, on Metzerott Road across from the System Administration building. 9 p.m. Information, 301-405-3001. Web, www.astro.umd.edu/openhouse.

Sept. 11 -- Sky-watching at Sky Meadows State Park near Delaplane, Va. For information call 540-592-3556. Also takes place Oct. 2.

Sept. 12 -- Having found quarters to accommodate larger crowds, the Northern Virginia Astronomy Club will present club members' photographs of the Aug. 11 total solar eclipse. The group meets at Lecture Hall No. 1 on the campus of George Mason University in Fairfax. 6 p.m. You may park in lots F and G, where parking is free on Sundays.

Sept. 18 -- Join the National Capital Astronomers and the National Park Service as they explore the heavens from the field located at Military and Glover roads NW, near the Rock Creek Nature Center. Telescopes will be set up. 8 p.m. Information, 202-426-6829.

Sept. 20 -- Astronomer Andrew Harris talk about "Astronomy's Practical Side: Where on Earth Am I?" at the University of Maryland astronomy department's open house. Sky-viewing following the lecture. 9 p.m.

Sept. 23 -- Cosmic debris hits Earth from time to time, sometimes creating generous amounts of natural damage. Learn all about meteorites as the Montgomery College Planetarium presents the lecture, "When the Sky Falls." The planetarium, in Takoma Park, is located on Fenton Street. Free parking in the faculty lot. 7 p.m. Information, 301-650-1463.

Oct. 2 -- John Graham of the Carnegie Institution of Washington's department of terrestrial magnetism will speak at the regular meeting of the National Capital Astronomers. At the Lipsett Amphitheater in the Clinical Center (Building 10) of the National Institutes of Health in Bethesda. 7:30 p.m.