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The October Sky at Night

Dr. Wayne Wooten
Professor of Astronomy
Escambia Amateur Astronomers' Association

For October, the Moon will be full moon on the 4th, this is the "Harvest Moon", closest to the Autumnal Equinox in late September. The first two weeks find the moon waning in the morning sky. Last quarter moon is October 1th and lies just south of Mars the following morning, and the waning crescent moon passes six degrees south of Saturn and much brighter Venus on October 16th, and seven degrees south of Mercury on October 17th. New Moon is on October 18th. Halloween finds the moon just past first quarter on the 26th, so the waxing gibbous moon and Jupiter in the south make for sharing telescopic views with the trick or treaters in the evening twilight.

While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up into deep space, far beyond our own Milky Way, binoculars are better for spotting specific deep sky objects. For a detailed map of northern hemisphere skies, about September 30th visit the website and download the map for October 2009; it will have a more extensive calendar, and list of best objects for the naked eyes, binoculars, and scopes on the back of the map.

Jupiter dominates the southern sky just above the tail of Capricornus the sea goat. Any small scope will reveal what Galileo marveled at 400 years ago this month; four large moons, all bigger or similar to ours in size, orbit it in a line along Jupiter's equator. So get out the old scope, and focus on Jupiter for a constantly changing dance of the moons around the giant world. Bigger scopes real much detail in its clouds, including the attached Great Red Spot

Venus dominates the morning now, and plays an interesting game of tag with Mercury and Saturn in the dawn. On October 1, Venus is above much fainter Mercury, which in turn is above faint Saturn 45 minutes before sunrise.

Mercury passes Saturn very closely on October 8th, and the most striking grouping is on October 10, with the three planets equally spaced and Saturn in the middle. Venus passes Saturn on October 13, and the waning crescent Moon joins the club on October 16th, passing just south of Venus, and by Mercury (but very difficult to spot in the dawn) on October 17th. These fine groupings are easy to capture with any tripod mounted digital camera in nightshot mode, so see if you can capture the fine sequence of planetary "dancing in the dawn".

The Big Dipper falls lower each evening. By the end of October, it will be only the three stars in the handle of Dipper still visible in the northwestern twilight. By contrast, the Little Dipper, while much fainter, is always above our northern horizon here along the Gulf Coast.

To the southwest, Antares and Scorpius also set soon after twilight, and will be gone by month's end. East of the Scorpion's tail is the teapot shape of Sagittarius, which marks the heart of our Milky Way galaxy. Looking like a cloud of steam coming out of the teapot's spout is the fine Lagoon Nebula, M-8, easily visible with the naked eye. This stellar nursery is ablaze with new stars and steamers of gas and dust blown about in their energetic births. In the same binocular field just north of the Lagoon is M-20, the Trifid Nebula.

The brightest star of the northern hemisphere, Vega dominates the sky overhead. To the northeast of Vega is Deneb, the brightest star of Cygnus the Swan. To the south is Altair, the brightest star of Aquila the Eagle, the third member of the three bright stars that make the Summer Triangle so obvious in the NE these clear autumn evenings.

To the east, the square of Pegasus is a beacon of fall. South of it lies the only bright star of Fall, Fomalhaut. If the southern skies of Fall look sparse, it is because we are looking away from our Galaxy into the depths of intergalactic space.

The constellation Cassiopeia makes a striking W, rising in the NE as the Big Dipper sets in the NW. Polaris lies about midway between them. She contains many nice star clusters for binocular users in her outer arm of our Milky Way, extending to the NE now.

Her daughter, Andromeda, starts with the NE corner star of Pegasus'' Square, and goes NE with two more bright stars in a row. It is from the middle star, beta Andromeda, that we proceed about a quarter the way to the top star in the W of Cassiopeia, and look for a faint blur with the naked eye. M-31, the Andromeda Galaxy, is the most distant object visible with the naked eye, lying about 2.5 million light years distant. It is a bigger version of our own Galaxy, which it may collide with about three billion years from now.

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