For October, the first quarter moon is in Sagittarius on October 2nd, and waxing gibbous moon below Saturn on October 5th. Almost full, it passes below Jupiter in SE on October 8th, and the Full "Hunter’s" Moon is October 9th. The waning gibbous moon passes above Mars in the dawn on October 15th, and is last quarter on October 17th. The old moon is above Mercury in the dawn on October 23, and very close to Mercury (use binocs about 30 minutes before sunrise) on October 24. The first quarter moon will make a telescopic treat for Halloween on October 31st, with Saturn and Jupiter also out to share with the kids in the neighborhood. Set up your telescope!
Mercury is low in the dawn sky in October. Venus lises behind the Sun all month. Mars is in Taurus the bull, rising about midnight, and will get much brighter and come to opposition early this December, the best time to observe it in the next two year. Jupiter reached opposition last month, and is well placed for viewing in the east and the brightest object in the night sky now. Saturn is in the tail of Capricornus, and well up at sunset in the SE.
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. Saturn lies above of the pour spout now. 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.
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 of Altair lies tiny Delphinus, a rare case of a constellation that does look like its namesake.
To the south, Saturn is in the head of Capricornus, and Jupiter above its tail. Aquarius and Pisces are among the faintest of the zodiacal constellations, and need dark skies to pick out. Fomalhaut is the only first magnitude star of the SE fall sky, and stands alone above the SE horizon now.
To the east, the square of Pegasus is a beacon of fall. 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.
Below the head of Pegasus is Aquarius, the Water Carrier. Below his western foot is the only bright star of the southern fall sky, Fomalhaut. It means the "mouth of the fish", and carries on the watery grouping of Pisces the Fish (home to Jupiter now), Capricornus the sea goat (with Saturn in its tail), Cetus the Whale in the SE, and Grus the Crane due south now. It is just north of Fomalhaut we find our beautiful "Eye of God", the Helical Nebula, NGS 7293, which is very dim in big binoculars, but half as big as the full moon. Our own sun will probably pass though this stellar striptease about 5 billion years from now, after it swells up into a red giant and devours the inner planets.
Below Andromeda is her hero, Perseus. In his hand is a star most appropriate for Halloween, Algol. This star "winks" at us for six out of every 70 hours, which Arabic astronomers centuries ago found spooky, hence naming it "the ghoul". We know today it is an eclipsing binary system, with the larger, cooler orange star covering 80% of its smaller, hotter neighbor during the "wink". At the foot of Perseus, the hero of "Clash of the Titans" is the fine Pleiades star cluster, the "seven sisters" that reveal hundreds of cluster members in large binoculars. This might be the best object in the sky for binocular users.
Winter will be coming soon, and in the NE we see yellow Capella rising. It is the brightest star of Auriga the Charioteer, and pair of giant stars the same temperature as our sun, but at least 100X more luminous and about 10X larger than our sun. It lies about 43 light years distant. A little farther south, below the Pleiades, orange Aldebaran rises. It is the eye of Taurus the bull, with the V shaped Hyades star cluster around it making the head of the bull. This colorful giant star is only 2/3 as hot as our yellow sun, but 44X times larger and at 65 light years distant, one of the closest of these monster stars.
