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The Sky This Week - 2012 September 18 - 25

Observe the Moon (and give it a wink for Neil!)

The Moon, 2009 NOV 22, 23:45 UT
Imaged with a 50mm (2-inch) f/10 "Galileoscope"
and a Canon PowerShot A95 digital camera
from Alexandria, VA

The Moon waxes in the evening sky this week, with First Quarter occurring on the 22nd at 3:41 pm Eastern Daylight Time. Skywatchers with a clear western horizon may be able to spot the very slender crescent Moon just above the southwestern horizon between fading Saturn and ruddy Mars at dusk on the 18th. On the following evening Luna lies just over a degree to the east of Mars. She spends the rest of the week coursing along the southern reaches of the Ecliptic courting the setting stars of summer before entering the vast star-poor reaches of the autumnal constellations.

September 22nd has been designated as "International Observe The Moon Night", a special evening to look at and learn about our closest neighbor in space. It’s a great opportunity to dust off that old telescope and get acquainted with the only other world visited by humans. I often say that the Moon is "looked over, then overlooked" by fledgling amateur astronomers since nothing much ever changes there, but careful observation will almost always reveal surprises to the patient observer. The Moon is a great target for small telescopes, spotting scopes, and even binoculars, all of which will transform Luna from something hanging in the sky to a place that has some truly amazing topography. With the recent passing of Neil Armstrong interest in the Moon is once again on the rise as we once again look back on those stark images made on the lunar surface. Take a few minutes on this evening and give the Moon a look and a wink for Neil!

The 22nd also happens to be the date of autumnal equinox, which occurs at 10:49 am EDT. At this time the Sun stands directly over the Earth’s equator just off the northeast coast of Brazil. Although the equinox officially marks the beginning of the astronomical season of autumn, the duration of night doesn’t exceed that of daylight until the 26th due to a combination of atmospheric refraction and the Sun’s apparent disc. However, it is one of the times of the year when the times of sunrise and sunset change most rapidly, so most of us will quickly notice the shortening days.

Early in the week you still have a few hours to enjoy the departing stars of summer and the brightest parts of the Milky Way before moonlight washes the galactic glow out. The bright stars of the Summer Triangle straddle the meridian at 9:00 pm, offering a couple of hours in the evening for you to explore the star clouds of our home galaxy. By midnight the more subdued star patterns of the autumn sky take over and we have to look a little harder to find treasures in the "deep sky". However, there are gems to be found here, and among those is the Andromeda galaxy, the closest major galaxy to the Milky Way. You can locate it yourself between the W-shaped constellation of Cassiopeia and the "Great Square" of Pegasus.

The planetary offerings of the early evening are now pretty meager. Saturn is very low in the southwest at dusk and sets by the end of evening twilight. Mars is still hanging tough in his race against the advancing Sun, but he sets less than an hour after Saturn. Your best chance to spot him will be on the 19th, when the crescent Moon pays him a visit.

If you want to see a bright planet you’ll need to wait for the wee hours. Giant Jupiter rises shortly before 11:00 pm, and by midnight he should be plainly visible in the east. We’re still several weeks away from his opposition, but you can now take advantage of the later times of sunrise to spot him almost overhead in morning twilight.

Venus is also very prominent in the pre-dawn sky where she has been dazzling early morning commuters with her brilliance. She will continue to brighten the morning sky for the rest of the year as she steadily moves eastward into the stars of the constellation Leo, the Lion.