Can you spot an ancient moon?

Sporadic or not?

September nights offer a nearly unparalleled view of sporadic meteors. These apparently random bits of dust burn up in a blaze of glory when they strike our atmosphere at a few dozen miles per second. Most get incinerated at an altitude of 50-70 miles.

Part of what makes September a good month for viewing sporadic meteors is the dearth of major meteor showers. This month provides a few minor showers, however, with the Alpha Aurigids probably at the top of the list. This shower peaks the morning of September 1, when observers at dark sites can expect to see roughly 7 meteors per hour, matching the sporadic rate.

How can you tell a shower meteor from a sporadic? The Alpha Aurigids all arrive from the same direction in space. These meteors appear to radiate from a point near the bright star Alpha Aurigae (better known as Capella), hence the shower’s name. Sporadics, on the other hand, come from random directions.

The best time to view the Alpha Aurigids shower is after midnight, when we’re on Earth’s leading hemisphere as we orbit the Sun. Auriga lies high in the early morning sky, and the First Quarter Moon sets around midnight. A secondary shower – the Delta Aurigids – peaks September 9, but the Moon is then just past full, and viewing will be difficult.

THE ALPHA AURIGID METEOR SHOWER boasts around 7 meteors per hour at it peak September 1, when the Moon will be gone from the morning sky.

Spy an old Moon

Seeing the Moon within a day or so of its new phase is a challenge that many backyard observers embrace. Viewing a slender crescent set against a multi-hued twilight sky is a sight not soon forgotten. Timing is critical for such views, and opportunities don’t arise every month at every location. The Moon must reach new phase approximately 24 hours before an evening sighting or 24 hours after a morning sighting, and it must be more than a degree or two high. Clear skies and a flat, unobstructed horizon also prove invaluable.

North American observers have a good chance this month to see an old Moon, and a bright object lies nearby to guide them. Part of the reason for the favorable circumstances is the nearly vertical angle the ecliptic makes to the eastern horizon on mornings this time of year. Essentially all of the Moon’s angular distance from the Sun translates into altitude above the horizon.

For observers in the Midwest, the Moon is 24 hours from new phase the morning of September 21. Venus, which shines at magnitude -3.8 and is easier to see, lies just 1º away then. Grab your binoculars, and carefully scan the region just to Venus’ right. Observers farther east will see the Moon an hour earlier; on the West Coast, the Moon will be 22 hours from new this morning. Venus rises about 50 minutes before the Sun, and the sky will brighten quickly. Of course, lucky observers in South America and western and southern Africa have a chance to see the actual New Moon a day later, when it appears in silhouette against the Sun’s face during an annular solar eclipse.

A THIN CRESCENT MOON HANGS LOW in the east before dawn September 21, imitating this 27-hour-old Moon seen June 7, 2005.