This Week's Sky at a Glance, November 17 – 26

FRIDAY, NOVEMBER 17

■ Look low in the south-southwest at nightfall for the waxing crescent Moon. It forms a huge, nearly equilateral triangle with Saturn far to its upper left and Altair far to its upper right. Each side of the triangle is nearly four fists at arm's length long.

■ After it's fully dark, look high in the northeast for W-shaped Cassiopeia. The W is standing on end. Below it sprawls Perseus. To find the famous Double Cluster in Perseus, count down the segments of the W starting from the top. The third segment points almost straight down. Follow that direction down by twice its length, and there you are. Binoculars show the little gray cluster-pair fairly easily.

But Perseus has many other open clusters! One of the nicest is M34 between Algol and Gamma Andromedae (just off the right edge right of the photo above). Use the finder chart with Matt Wedel's Binocular Highlight column in the November Sky & Telescope, page 43. Using large binoculars or a small telescope, Matt writes, "Look for a compact, boxy core surrounded by a ragged outer loop of eight or so 8th- to 10th-magnitude stars. I envision [M34] as a medieval city, ringed by a strong defensive wall. The illusion of a dark moat between the core and the loop is most pronounced in 7x binos [in a black sky], whereas 15 x 70s may fill the gap with a dusting of faint suns, at least in very good conditions."

The Double Cluster itself is closely surrounded by an array of telescopic double stars, obscure clusters, and little asterisms. See Ken Hewett White's Suburban Stargazer column starting on page 54 of the November issue.

■ The Leonid meteor shower, very weak in recent years, should be at its most active late tonight. Your best chance of catching any Leonids at all is in the hour or two before the first light of dawn, when the shower's radiant is highest. There will be no Moon.

SATURDAY, NOVEMBER 18

■ Orion now clears the east horizon around 8 p.m., depending on how far east or west you live in your time zone. Above Orion shines orange Aldebaran. Above Aldebaran is the little Pleiades cluster, the size of your fingertip at arm's length.

Far left of Aldebaran and the Pleiades is bright Capella.

Down below Orion, Sirius rises around 10 p.m. Sirius always follows along two hours behind Orion, no matter where in the sky they are.

SUNDAY, NOVEMBER 19

■ This evening and tomorrow evening the Moon passes Saturn while going through first-quarter phase, as shown below. Here are the perhaps the two most popular telescopic objects in the sky, waiting for you just a few degrees apart.

MONDAY, NOVEMBER 20

■ First-quarter Moon (exact at 5:50 a.m. EST Monday morning). The Moon accompanies Saturn more closely than it did yesterday, as shown above.

■ The tiny black shadow of Io crosses Jupiter's face from 9:16 to 11:26 p.m. EST, moving across Jupiter from east to west. The side of Jupiter without the Great Red Spot will be facing us.

TUESDAY, NOVEMBER 21

■ Algol should be at minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:55 p.m. EST; 7:55 p.m. PST. Algol takes several additional hours to fade and to rebrighten.

WEDNESDAY, NOVEMBER 22

■ The east (left) side of the Great Square of Pegasus points down to the Moon this evening.

■ And the Moon itself forms a bigger, wide rectangle with (counting clockwise) Saturn three fists to its right, Fomalhaut below Saturn, and Beta Ceti left of Fomalhaut.

THURSDAY, NOVEMBER 23

■ Does the Sun already seem to be setting about as early as it ever will? Correct. We're still a month from the winter solstice — but the Sun sets its earliest around December 7th if you're near latitude 40° north, and already the Sun sets within only about 2 minutes of that time.

A surprising result of this: The Sun actually sets a trace earlier on Thanksgiving than on Christmas — even though Christmas is famously close to solstice time!

This offset of earliest sunset from the solstice date is balanced out by the opposite happening at sunrise: The Sun doesn't rise its latest until January 4th. Blame the tilt of Earth's axis and the eccentricity of Earth's orbit.

FRIDAY, NOVEMBER 24

■ The Moon has moved on to the next giant planet, shining near Jupiter this evening and tomorrow evening as shown below.

■ Algol should be at minimum light for a couple hours centered on 7:44 p.m. EST Friday evening.

SATURDAY, NOVEMBER 25

■ As the stars come out, the Cassiopeia W stands on end (its fainter end) high in the northeast. Watch Cas turn around to become a flattened M, even higher in the north, by late evening.

SUNDAY, NOVEMBER 26

■ The Moon is full both this evening and tomorrow evening (because it's exactly full at 4:16 a.m. Monday morning EST). This evening, the glary Moon is just 1° or 2° from the Pleiades for North America. Bring binoculars.

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This Week's Planet Roundup

Mercury is still hidden low in the afterglow of sunset.

Venus, a brilliant magnitude –4.3, shines as the "Morning Star" in the east-southeast before and during dawn. It rises a good 2 hours before dawn's first light, a weird late-night apparition coming up over the east horizon.

Mars is out of sight behind the glare of the Sun. It won't emerge into dawn view until around the end of January.

Jupiter (magnitude –2.8, in Aries) dominates the east during early evening and stands highest in the south around 10 or 11 p.m. It sets in the west before dawn begins. In a telescope Jupiter is still a big 48 or 47 arcseconds wide.

Saturn (magnitude +0.8, in dim Aquarius) glows yellowish high in the south at nightfall. It moves lower toward the southwest as evening grows late. Fomalhaut, similarly bright, twinkles almost two fists at arm's length to Saturn's lower left.

Saturn this week is at quadrature with the Sun (exactly so on November 22nd).

Uranus, magnitude 5.6 in Aries, hides 13° east of Jupiter. It's just past its November 13th opposition. In a telescope at high power Uranus is a tiny but distinctly nonstellar ball, 3.8 arcseconds in diameter. See the finder charts for Uranus in the November Sky & Telescope, pages 48-49.

Neptune, magnitude 7.8 at the Aquarius-Pisces border, is high in early evening 24° east of Saturn. Neptune is only 2.3 arcseconds wide: harder to resolve as a ball than Uranus, but definitely nonstellar at high power.

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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 Standard Time (EST) is Universal Time minus 5 hours. UT is also known as UTC, GMT, or Z time.

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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.

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), which shows all 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 mag 9.75). And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet 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. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.

Can computerized telescopes replace charts? Not for beginners I don't think, especially not 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 the sky. 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."

But finding a faint telescopic object the old-fashioned way with charts isn't simple either. Learn the tricks at How to Use a Star Chart with a Telescope. 

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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.

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"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

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