Venus has been remarkably consistent all summer long, emerging as a brilliant light in the western sky at dusk and setting just before 9 p.m. This trend continues in October.
Look for Venus as it gets dark. Venus is that airplanelike dot about a fourth of the way up in the west as it gets dark. Venus emerges from the twilight around 6:30 p.m. and sets around 8:30 p.m. throughout October.
Look for the waxing crescent moon close to Venus on the nights of Oct. 7 and 8. Then, on the evenings of Oct. 15-17, look for Venus just above the reddish first-magnitude Antares in Scorpius. On the night of the 16th, when the two dots of light will appear closest to each other, Venus will be only 1.6 degrees above Antares, less than the thickness of a finger at arm’s length. Venus will be about 100 times brighter than Antares.
Meanwhile, the International Space Station will rise near Venus a few minutes before 7 p.m. on Oct. 6 and arch toward the northeast.
Saturn has been a constant companion in our mid-evening skies all summer, but its time is coming to an end. You might still catch Saturn low in the west at nightfall for the first two weeks of October. If you look west around 7 p.m. in early October, Saturn is about 10 degrees above the western horizon, or the width of your palm at arm’s length.
Find Mercury near the horizon. Saturn is the dot above it, somewhat fainter. Saturn sets by 8 p.m. at the start of October; by Oct. 20 it sets just before 7 p.m., meaning we’ve pretty much lost it in the sun’s light.
The best night for spotting Saturn in October will be Oct. 6, when the slender crescent moon will be right between Saturn (on top) and Mercury (below the moon). Look for this sight just before 7 p.m. But look fast — Mercury sets by 7:25.
Mercury is the third planet in the western skies at dusk in October. It’s visible for the first two weeks of the month. It’s quite bright but you don’t have much time to see it. Look west around 7 p.m. — it’s the bright light about 4 degrees (two fingers at arm’s length) above the western horizon. It will set by 7:30 p.m. Since Mercury is so low, make sure you have a totally flat western horizon. Looking over the sea is good. By about Oct. 20, we’ll lose Mercury in the sunset light.
Jupiter is by far the brightest morning dot in October. At the start of the month, Jupiter rises at 12:30 a.m. and is two-thirds of the way up in the east at daybreak. By the end of the month, Jupiter rises by 10:45 p.m. and is in the top of the sky at daybreak.
While Jupiter is the brightest dot of light in the morning, it is also accompanied by the brilliant winter stars. The planet is actually in the constellation of the Gemini, with its bright stars Castor and Pollux. Jupiter is about 25 times brighter than Pollux, Gemini’s brightest star. To Jupiter’s right and slightly higher is the constellation Orion the Hunter. At right and slightly lower is Sirius, the brightest star in the sky.
Look for the waning gibbous moon next to Jupiter early in the morning of Oct. 26 and the following morning, when the moon will be a last quarter moon.
Mars remains pretty dim in the morning sky in October. It rises in the east at 3 a.m. in early October and at 2:30 a.m. at the end of the month. Mars spends the month in Leo the Lion, whose brightest star, Regulus, is a little brighter than Mars. In the first two weeks of October, Mars will appear a little closer to Regulus every night; on the morning of the 15th, Mars and Regulus will be less than 1 degree apart, which is less than the width of your pinky finger at arm’s length. Regulus has a slightly bluish color; Mars does have a distinctive orange-red tint. Early on Tuesday (about 4 a.m.), look for a very old waning crescent moon down below Mars.
Mars, Comet Ison
Comet Ison will appear to be close to the planet Mars in October, and possibly visible in small telescopes. The comet’s visibility in October will be a sign for whether the comet will be spectacular in late November.
Comet Ison was discovered in September 2012 and there were some comments about it being "the comet of the century." That said, when the comet was picked up in telescopes in mid-August after being lost in the sun’s glare for more than two months, it appeared about six times fainter than expected. Astronomers are being guarded about what to expect when the comet peaks later in the fall.
October Sky Map
We have lost the Big Dipper and Scorpius, both below the horizon. Sagittarius is still visible low in the west. The constellation is also called The Teapot; the eight stars that make the core of the constellation are quite bright.
Halfway down in the western sky we have the Summer Triangle, made of one bright star pulled from each of three constellations: Vega from Lyra the Harp, Deneb from Cygnus the Swan, and Altair from Aquila the Eagle.
We can now also find all of the constellations that tell the story of Perseus and Andromeda. This includes Perseus himself, just rising in the northeast; Pegasus the flying horse; Andromeda, the maiden he rescued; and Andromeda’s parents, Queen Cassiopeia and King Cepheus.
The first stars of winter already are poking their heads above the eastern horizon, Auriga the Charioteer and Taurus, which includes the famous cluster Pleiades.
