Monday, September 1, 2014

The September Sky and Tonight's Sky for September 1

The coming of September also signals the arrival of the Autumnal Equinox, which means that, by month's end, the night will once again be longer than the day. Also, with the equinox upon us, the most dramatic differences in solar movement (and thus length of day) will also occur, which means that, at least at the start of the night, the September sky is not all that different than it is in August. In all, the shorter nights combined with the lingering presence of the summer stars and warmth makes for what is arguably the best time for astronomy in the entire year.

Cool Constellations
With the advent of September, the spring constellations are rapidly saying goodbye, with Virgo the next major constellation to disappear. Also getting low in the Southwest is Libra and Bootes and Corona are now just about due West at nightfall. In the North, the Big Dipper continues its dive, flattening out as it starts to approach the horizon. Perhaps the best part of the September sky is that one doesn't need to stay up late to see all the best sights of summer. At nightfall, Hercules is still near zenith, the Summer Triangle (Lyra, Cygnus, and Aquila along with hangers-on Saggita and Delphinus) is at zenith, Scorpius is due South with Ophiuchus and Sagittarius on either side, both still well-placed for observing. Also, the Milky Way is at its best positioning right after nightfall, too. For people who like to stay up late (or get up extremely early) a fall preview in the form of Pegasus, Pisces, Cetus, Andromeda, Aries, Capricorn, Aquarius, and even Perseus is on tap in the wee hours of the morning while, by month's end, the bright stars of winter in the form of Orion, Auriga, Taurus, and Gemini are visible, too. .

Planetary Perceptions
In terms of planets, September isn't shaping up to be all that great of a month despite all of the 5 classical planets being visible. Why? Most of the planets are rather close to the Sun. Starting in the evening, both Mars and Saturn are visible, though both are now pretty much dusk objects from all but the most unobstructed viewing locations. In the predawn sky, Venus is still rather well-placed at month's start but, nothing being forever, this exceptionally long apparition of Venus will be starting to come to a conclusion as the planet begins a dramatic drop toward the Sun's glare as the month unfolds. On the other hand, Jupiter, which just reappeared from behind the Sun as a morning planet in late July continues its rise out of the solar glare and is, by month's end, an easy telescopic target under dark skies for night owls and early birds in the Eastern predawn sky. Mercury? Well, it's up at the start of the month but, thanks to the angle of the ecliptic plane, it's about as bad as an appearance as is geometrically possible, barely popping over the Western horizon in a very poor evening appearance.

Tonight's Sky for September 1: Sagittarius Due South at Dark

Want to see the constellation of Sagittarius but don't know where to look? Well, early September finds the Zodiac constellation just about due South about the time the sky gets truly dark, namely about 1 to 1 ½ hours after sunset. To see the constellation, head out and look due South for the easy to recognize teapot shape. As an added bonus, if you live under relatively dark skies, look for the hazy Milky Way, which looks like cosmic steam emanating from the Teapot's spout.

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