FRIDAY, OCTOBER 16
■ This is the time of year when, after nightfall, W-shaped Cassiopeia stands on end halfway up the northeastern sky — and when, off to its left in the north, the dim Little Dipper extends leftward from Polaris.
■ Jupiter's Great Red Spot should transit Jupiter's central meridian around 9:22 p.m. Eastern Daylight Time.
An hour later, at 10:23 p.m. EDT, Jupiter's moon Io reappears from eclipse out of Jupiter's shadow just east of the planet — very close to Callisto, with Europa and Ganymede somewhat farther out. A small telescope will show Io swelling into view over the course of a couple minutes, turning Callisto into an imitation double star.
■ New Moon (exact at 3:31 p.m. EDT).
SATURDAY, OCTOBER 17
■ Look closer at Cassiopeia high in the northeast, a W standing on end. The third segment of the W, counting down from the top, points almost straight down. Extend that segment twice as far down as its own length, and you're at the Double Cluster in Perseus. This pair of star-swarms is dimly apparent to the unaided eye in a dark sky (use averted vision), and it's visible from almost anywhere with binoculars. It's lovely in telescopes.
SUNDAY, OCTOBER 18
■ After dark, Capella sparkles low in the northeast. The farther north you are, the higher it will be. (From the southern U.S., you'll have to wait till a little later in the evening.) To the right of Capella, by about three fists at arm's length, the Pleiades are climbing into view. And soon Aldebaran will rise below the Pleiades.
Upper right of Capella, and upper left of the Pleiades, the stars of Perseus lie astride the Milky Way.
MONDAY, OCTOBER 19
■ Vega is the brightest star very high in the west these evenings. Less high in the southwest is Altair, not quite as bright. Just upper right of Altair, by a finger-width at arm's length, spot little orange Tarazed. Down from Tarazed runs the stick-figure backbone of the constellation Aquila, the Eagle. His wingtips are upraised, in the style of the Eagle Scout emblem. Altair is his sharp eye.
■ Look to Altair's upper left by a little more than a fist at arm's length, and there's the faint little constellation Delphinus, the Dolphin, leaping in the edge of the Milky Way.
■ Delphinus sports some interesting, little-known telescopic objects — from the Toadstool asterism Thompson 1 near Iota Delphini, to the brightest non-Messier globular cluster in the northern celestial hemisphere (it's 9th magnitude), to the elusive NGC 6928 galaxy cluster (for big scopes; they're magnitude 12.2 and fainter). Explore here using the Deep-Sky Wonders column and charts in the October Sky & Telescope, page 56.
TUESDAY, OCTOBER 20
■ The Great Square of Pegasus is high in the east-southeast after dark — still, for now, balancing on one corner (for the world's mid-northern latitudes).
■ The Orionid meteor shower, modest but definitely there, will be active in the early-morning hours for several days. It should be at its strongest from about 1 or 2 a.m. until dawn local time both Wednesday and Thursday mornings. You might see about 10 meteors an hour under excellent dark-sky conditions, the closer to dawn the better. The Moon will have long set. The shower's radiant is at the top of Orion's Club, which gets higher through the pre-dawn hours. The higher a meteor shower's radiant, the more meteors appear in all parts of the sky.
If the late night is clear bundle up very warmly (think radiational cooling), bring a reclining lawn chair to a spot with an open view and no local lights to get in your eyes, lie back, and look up into the stars. The best direction to watch is the darkest part of your sky, probably straight up. Be patient. Astronomy teaches patience.
WEDNESDAY, OCTOBER 21
■ The Moon, nearing first quarter, shines in a line with Saturn and Jupiter. It's to their lower right, as shown at the top of this page.
■ It's mid-October, so Deneb has replaced Vega as the zenith star after nightfall (for skywatchers at mid-northern latitudes). And so, necessarily, Capricornus has replaced Sagittarius as the zodiacal constellation due south.
■ Jupiter's Great Red Spot should transit the planet's central meridian around 8:31 p.m. EDT.
THURSDAY, OCTOBER 22
■ Now the Moon forms a rather tight triangle with Jupiter and Saturn, as shown at the top of this page.
■ This is the time of year when the Big Dipper lies down horizontal low in the north-northwest during evening. How low? The farther south you are, the lower. Seen from 40° north (New York, Peoria, Denver) even its bottom stars twinkle nearly ten degrees high. But at Miami (26° N), the entire Dipper skims along out of sight just below the northern horizon.
FRIDAY, OCTOBER 23
■ First-quarter Moon, exact at 9:23 a.m. Eastern Daylight Time. By evening, about half a day later (for North America), the Moon's terminator will have become just a little bit convex. The Moon will shine in dim Capricornus left of Jupiter and Saturn at dusk, and upper left of them as the evening grows late.
■ Jupiter's Great Red Spot should transit Jupiter's central meridian around 7:10 p.m. Pacific Daylight Time. (The West Coast is having its good view of Jupiter around then.)
SATURDAY, OCTOBER 24
■ The Moon, a day and a half past first quarter now, shines in Capricornus. It forms the top of a very wide, flat, almost isosceles triangle with Fomalhaut, about two fists to the Moon's left and a little lower, and Saturn, about two fists to the Moon's right and a little lower. (Brighter Jupiter shines a bit beyond Saturn).
Fomalhaut and Saturn balance at the same height around 9 p.m. daylight-saving time, depending on your location.
■ The Ghost of Summer Suns. Halloween is approaching, and this means that Arcturus, the star sparkling low in the west-northwest in twilight, is taking on its role as "the Ghost of Summer Suns." What does this mean? For several days centered on October 25th every year, Arcturus occupies a special place above your local landscape. It closely marks the spot where the Sun stood at the same time, by the clock, during hot June and July — in broad daylight, of course!
So, as Halloween approaches every year, you can see Arcturus as the chilly ghost of the departed summer Sun.
This Week's Planet Roundup
Mercury is hidden in the glare the Sun.
Venus (magnitude –4.0, between Leo and Virgo) rises in the east in deep darkness about 1½ hours before dawn begins. Once dawn is under way, Venus is in fine view as the bright "Morning Star" in the east. Look about a fist at arm's length to its left or upper left for 2nd-magnitude Denebola, Leo's tail-tip.
In a telescope Venus is a dazzling little gibbous ball, just 14 arcseconds from pole to pole.
Mars (about magnitude –2.4, in Pisces) passed through opposition on October 13th and is still much larger and brighter than we usually see it. This week it shrinks just a little, from 22 to 21 arcseconds in diameter. But it climbs into fine, high telescopic view earlier in the night!
At dusk Mars glares fiery orange, a trace more than Jupiter-bright, low in the east. It's high in the southeast by 10 p.m. daylight-saving time, and it's highest at its telescopic best by midnight, blazing in the south.
See Bob King's "A Great Year for Mars" in the October Sky & Telescope, page 48, and his Behold Mars! article online. To get a map of the side of Mars facing Earth at the date and time you'll observe, you can use our Mars Profiler. The map there is square; remember to mentally wrap it onto the side of a globe. (Features near the map's edges become very foreshortened; compare with the images above.)
Jupiter and Saturn (magnitudes –2.2 and +0.5, respectively) shine in the south-southwest in late dusk. Get your telescope on them early before they sink lower toward the southwest later in the evening.
Jupiter is the bright one; Saturn is 6° to its upper left. Watch them creep toward each other for the rest of the fall. They'll pass just 0.1° apart at conjunction on December 21st, low in twilight, as fall turns to winter.
See Bob King's Stormy Times on Jupiter. And you can follow the interplay of Jupiter with its moons and their shadows, and find all the transit times of Jupiter's Great Red Spot, using the Celestial Calendar section of the October Sky & Telescope.
Uranus (magnitude 5.7, in Aries) is well up in the east by 9 or 10 p.m. daylight-saving time, about 20° east of Mars. Uranus is only 3.7 arcseconds wide, but that's enough to appear as a tiny fuzzy ball, not a point, at high power in even a small telescope.
Neptune (magnitude 7.8, in Aquarius) is a little higher in the south at that time. Neptune is 2.4 arcseconds wide, harder to resolve except in good seeing. Check in on them when you're done with Mars: Finder charts for Uranus and Neptune.
All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.
Eastern Daylight Time, EDT, is Universal Time minus 4 hours. (Universal Time is also known as UT, UTC, GMT, or Z time.)
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy.
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And be sure to read how to use sky charts with a telescope.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically, meaning heavy and expensive. And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."
Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the heavens above. It's free.
"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
— Carl Sagan, 1996
"Facts are stubborn things."
— John Adams, 1770