FRIDAY, OCTOBER 10
■ In tonight’s sky W-shaped Cassiopeia stands on end high in the northeast, halfway to the zenith. Off to its left in the north, the dim Little Dipper runs leftward from Polaris to Kochab, Polaris’s close equal, as shown below.
How much of the Little Dipper you can or cannot see is a quick check of your light pollution. Here’s a closeup of the Little Dipper, with the magnitudes of stars to look for from mag 2.0 to 6.4:
■ Jupiter’s moons Io and Europa will both be casting their tiny black shadows onto Jupiter’s face early Saturday morning, from 4:42 to 6:53 a.m. EDT; 1:42 to 3:53 a.m. PDT. For a complete listing of these events worldwide during October, see “Jupiter’s Double Shadow Jamboree” in the October Sky & Telescope, page 48.
SATURDAY, OCTOBER 11
■ As October proceeds, Deneb replaces Vega as the zenith star of early evening (for skywatchers at mid-northern latitudes). Accordingly, Capricornus replaces Sagittarius as the zodiacal constellation having its best display in the south.
■ Before and during early dawn tomorrow the 12th, the almost-last-quarter Moon is on its way toward Jupiter, Pollux, and Castor, as shown below.
SUNDAY, OCTOBER 12
■ Algol should be at its minimum brightness tonight, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 12:42 a.m. EDT; 9:42 p.m. PDT. Algol takes several hours before and after to fade and to rebrighten. Comparison-star chart giving comparison-star magnitudes, with north up.
■ Last-quarter Moon tonight (exact at 2:13 p.m. Monday the 13th). In early dawn Monday morning the Moon stands between the stick figures of the Gemini twins (for the longitudes of the Americas), with Jupiter just below them.
■ Jupiter’s moons Io and big Ganymede will both be casting their shadows onto Jupiter’s face tonight from 11:11 p.m. to 1:29 a.m. EDT. Eastern and central North America will have a good view, but in the West, Jupiter will still be low or yet to rise.
MONDAY, OCTOBER 13
■ Can you still make out the Sagittarius Teapot low in the southwest right after dusk? It’s tipping far over now as it descends, as if pouring away from its spout the last of summer warmth. Your latitude governs how long it remains in view. As always, the farther south you are, the higher the Teapot.
■ Before dawn Tuesday morning the 14th, the Moon forms a roughly equilateral triangle with Jupiter and Pollux as shown in the illustration above.
TUESDAY, OCTOBER 14
■ Have you been watching Saturn with respect to the Great Square of Pegasus? Saturn is the brightest point in the east-southeast after dark. The Great Square, still tipped on one corner, stands to Saturn’s upper left in early evening. It turns to lie level straight above Saturn by about 11 p.m.
Last July, when Saturn was at the eastern end of its retrograde loop, the Square’s east (left) side pointed right at it. Now Saturn is nearing the western end of its retrograde loop, and it’s obviously way out of alignment with that line.
Saturn is so far away, and thus its retrograde loop is so small (7° long), that you might think the loop doesn’t matter for naked-eye skywatchers. But it does if you pay attention!
WEDNESDAY, OCTOBER 15
■ Ceres, the largest asteroid and the first discovered, remains in binocular range at magnitude 7.7. It’s now near Phi1 and Phi2 Ceti. Use the finder chart in the October Sky & Telescope, page 50. There, the tick marks on its path are for 0:00 UT on the dates indicated, which falls on the evening of the previous date for the Americas.
THURSDAY, OCTOBER 16
■ After dark, spot the W of Cassiopeia high in the northeast. It’s standing almost on end, as shown in the top illustration on this page.
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: twin cities of stars. Well, fraternal twins maybe.
FRIDAY, OCTOBER 17
■ This is the time of year when the Big Dipper lies down horizontal low in the north-northwest soon after dark. How low? The farther south you are, the lower. Seen from 40° north (New York, Denver) even its bottom stars twinkle nearly ten degrees high. But at Miami (26° N) the entire Dipper will skim along out of sight just below the northern horizon.
■ For West Coast and Hawaii telescope users, Jupiter offers two double-shadow transits early Saturday morning. Jupiter’s moons Io and Europa will both be casting their tiny black shadows onto Jupiter’s face from 3:42 to 5:49 a.m. PDT Saturday morning. Then 18 minutes later, Callisto’s shadow enters Jupiter’s limb at 6:07 a.m. PDT before Europa’s leaves the other side at 6:30 a.m. EDT.
By then it’s getting light in the western time zone. But Hawaiians have a good view of both double-shadow events. Subtract 3 hours from PDT to get Hawaii times.
SATURDAY, OCTOBER 18
■ A challenge in bright twilight. Mercury and Mars are in conjunction, 2° apart, very low in the west-southwest in the fading afterglow of sunset as shown above. Bring good binoculars, or a telescope with its lowest-power, widest-field eyepiece, to a site with a flat horizon to the west-southwest. Starting about 15 minutes after sunset, scan slowly just above the horizon.
Mercury is by far the brighter of the two at magnitude –0.2, not counting atmospheric extinction. If you catch Mercury, move upward 2° (about a third the width of the view in typical good binoculars). Mars is only magnitude +1.5, a fifth as bright as Mercury.
Good luck. If you manage to glimpse Mars, you’ll be one of the last few people on Earth to see it in its 2024-2025 apparition now drawing to a close.
■ Much easier: In Sunday’s dawn the thin Moon, just two days from new, shines about 4° to the right or upper right of bright Venus low in the east, as shown below.
SUNDAY, OCTOBER 19
■ The Orionid meteor shower may already be active in the hours before dawn Monday morning. This relatively long-lasting shower ought to peak on the morning of the 22nd. The sky is free of moonlight throughout. The shower’s radiant is at the top of Orion’s club. See the October Sky & Telescope, page 49.
■ Yet more double-shadow action on Jupiter! Io and Ganymede are both casting their little shadows onto Jupiter’s face tonight from 2:42 to 3:18 a.m. EDT. That’s 11:42 p.m. to 12:18 a.m. PDT, although for the West Coast Jupiter will still be low or unrisen.
This Week’s Planet Roundup
Mercury (magnitude –0.2) and Mars (magnitude +1.5) are very low in the bright afterglow of sunset. They’re in conjunction on the 18th and 19th, as shown near the top of this page.
Venus (magnitude –3.9) rises just before the beginning of dawn. Watch for it to come up due east. The thin waning crescent Moon accompanies it on the morning of the 19th.
Jupiter, magnitude –2.2 in Gemini, rises by midnight local daylight-saving time and dominates the east as the morning hours advance. Castor and Pollux shine above it. By the beginning of dawn the three stand very high in the south — with Procyon below them and Orion standing upright farther to their lower right.
Saturn (magnitude +0.8) is up in the east-southeast as night falls. It climbs through the evening. Spot it lower right of the Great Square of Pegasus in early evening, and directly below the Square by the time Saturn transits the meridian (due south) around 11 p.m. In a telescope its rings remain very nearly edge-on.
Uranus (magnitude 5.6, in Taurus 4° from the Pleiades) is well up by 9 or by 10 p.m. At high power in a telescope it’s a tiny but definitely non-stellar dot, 3.6 arcseconds wide.
Neptune is a telescopic “star” of magnitude 7.8, a dim pinhead just 2.4 arcseconds wide a few degrees from Saturn. Use the finder chart for Neptune with respect to Saturn in the September Sky & Telescope, page 49. With a pencil, put a dot on the path of each of the two planets for your date.
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 and graphics that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) is Universal Time minus 4 hours. UT is also known as 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 a more detailed 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.
For the attitude every amateur astronomer needs, read Jennifer Willis’s Modest Expectations Give Rise to Delight.
Once you get a telescope, to put it to good use you’ll need a much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas, in either the original or Jumbo Edition. Both show all 30,000 stars to magnitude 7.6, and 1,500 deep-sky targets — star clusters, nebulae, and galaxies — to search out among them.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many, as well as many more deep-sky objects. It’s currently out of print, but maybe you can find one used.
The next up, once you know your way around well, are the even larger Interstellarum Deep-Sky Atlas (with 201,000+ stars to magnitude 9.5 and 14,000 deep-sky objects selected to be detectable by eye in very large amateur telescopes), and Uranometria 2000.0 (332,000 stars to mag 9.75, and 10,300 deep-sky objects).
And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet (which many observers find more versatile) as to charts on paper.
You’ll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham’s Celestial Handbook. It was my bedside reading for a long time. An impressive more modern one is the big Night Sky Observer’s Guide set (2+ volumes) by Kepple and Sanner. The pinnacle for total astro-geeks is the new Annals of the Deep Sky series, currently at 11 volumes as it works its way forward through the constellations alphabetically. So far it’s up to H.
Can computerized telescopes replace charts? Not for beginners I don’t think, and not for scopes on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning how to explore the sky. 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 and a curious mind.” Without these, “the sky never becomes a friendly place.”
If you do get a computerized scope, make sure that its drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).
However, finding faint telescopic objects the old-fashioned way with charts isn’t simple either. Do learn the essential tricks at How to Use a Star Chart with a Telescope.
Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty’s monthly
podcast tour of the naked-eye 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; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.”
— John Adams, 1770
