This Week’s Sky at a Glance

Where to look for Comet ISON low in early dawn. On Saturday morning the 23rd, it's directly right of Mercury and Saturn. It's dropping lower and becoming much harder to detect every day! Mercury and Saturn are much brighter; start with them to find the spot to examine for the comet with binoculars or a wide-field telescope. The comet symbol is exaggerated.

For scale, these scenes are two or three times as wide as your fist held at arm's length.

The illustrations are free to reproduce anywhere with credit including a link to SkyandTelescope.com.

Getting much harder....
Comet ISON is becoming a lot harder to spot with binoculars or (better) a telescope as it moves lower in the brightening dawn — even as the comet brightens day by day, racing toward its November 28th perihelion. See our Latest Updates on Comet ISON and our press release (with free-for-use high-res graphics) Comet ISON Brightening as its Moment of Truth Nears.

Meanwhile, Comet Lovejoy C/2013 R1 remains much higher and easier to see in binoculars before dawn even begins. It's 5th magnitude and in Canes Venatici, south of the Big Dipper's handle. Use our finder chart.


Friday, November 22

  • The waning gibbous Moon is up in the east by about 10 p.m. tonight (depending on where you live). Look above it for bright Jupiter and, to Jupiter's left, Pollux and Castor. To the Moon's right twinkles Procyon. Much farther to the right, brighter Sirius is rising or soon to rise.

    Saturday, November 23

  • The eclipsing binary star Algol should be at minimum light, magnitude 3.4 instead of its usual 2.3, for a couple hours centered on 9:06 p.m. Eastern Standard Time. It takes several more hours to fade and to rebrighten.

    Sunday, November 24

  • During dawn Monday and Tuesday mornings, when you're preparing to use binoculars or a telescope to make one last pre-perihelion try for Comet ISON barely above the bright horizon, you'll find Mercury and fainter Saturn shining to the naked eye just 3/4° apart (at the times of dawn in North America). They're well above the spot to look for the comet: by 7° on Monday, 9° on Tuesday.

    In a telescope, Mercury will be a tiny, slightly gibbous disk 5.6 arcseconds in diameter (no bigger than Mars, high in the southeast), while Saturn is dimmer but much larger: 34″ across its rings. They're a nice consolation prize!

    Monday, November 25

  • Last-quarter Moon (exact at 2:28 p.m. EST). The Moon rises around 1 a.m. tonight. By dawn Tuesday morning it's high in the south, with Regulus to its right and Mars to its lower left.

    Tuesday, November 26

  • Jupiter's Great Red Spot should cross the planet's central meridian around 11:36 p.m. Eastern Standard Time tonight. The tiny black shadow of Jupiter's moon Io crosses the planet's face from 11:47 p.m. EST to 2:01 a.m. EST.

  • By about 2 a.m. Wednesday morning the waning Moon is up in the east with Mars shining to its left. By dawn Wednesday morning, they're high in the southeast.

    Wednesday, November 27

  • You may think you know Cassiopeia, but I bet you've never hunted its open cluster King 20 or teased apart the multiple star ADS 16795 just ½° to the cluster's west. And, the charming double star Struve 3022 shines in the same telescopic field. See Sue French's Deep-Sky Wonders in the November Sky & Telescope, page 56.

    The waning Moon passes Spica as it descends the dawn sky. (The Moon's position is drawn for the center of North America.)

    Thursday, November 28

  • Comet ISON comes to perihelion around 2 p.m. EST (19h UT). It's very unlikely to be bright enough to be detectable in the Sun's immediate glare. If you want to try, don't harm your eyes! Put the Sun behind something like a building corner or a streetlight fixture, not your wiggling finger. The apparent location of the comet will be within one solar diameter of the Sun's edge from about noon to 3 p.m. EST. The comet swings from due south of the Sun at 12:30 p.m. EST to closely southeast of it at 1:30 p.m. EST, due east at 2:20 p.m. EST, and farther northeast for several hours thereafter.

  • Jupiter's Great Red Spot should transit the planet's central meridian tonight around 1:14 a.m. EST (10:14 p.m. PST).

  • The waning Moon shines near Spica in the dawn Friday morning, as shown here.

    Friday, November 29

  • This is the time of year when the Great Square of Pegasus floats highest overhead at dinnertime. Its western side points far down almost to Fomalhaut shining in the south. Its eastern side points less directly down toward Beta Ceti (Diphda), less far below.

    What will have emerged from the comet's graze around the Sun? (The blue 10° scale bar is about the width of your fist at arm's length.)
    SkyandTelescope.com

    Saturday, November 30

  • Which rises first: bright Jupiter in the east-northeast, or bright Rigel in Orion's foot in the east-southeast? Both are up by about 8 p.m. depending on where you live. At the latitudes of the U.S. and southern Canada, Rigel comes first tonight. As far north as Paris (latitude 49°) and points north, Jupiter is first.

  • Sunday morning might already be time to try to pick up Comet ISON post-perihelion. But it will be very low above the dawn horizon. Saturn, the crescent Moon, and Mercury guide your way to the right spot, as shown at right. Bring binoculars or a wide-field scope.


    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 guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

    Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.

    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 (able to point with better than 0.2° repeatability, which means heavy and expensive). As Terence Dickinson and Alan Dyer say in their invaluable 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."


    This Week's Planet Roundup

    Jupiter on November 24th. Note the vivid orange color of the Great Red Spot now, and the massive white turbulence trailing far behind it in the South Equatorial Belt. South is up.

    Mercury and Saturn are together low in the dawn with Comet ISON passing nearby. Look very low in the east-southeast during dawn, far lower left of Spica. Mercury is magnitude –0.7; Saturn is one-third as bright at +0.6. They pass each other less than 1° apart on the mornings of the 25th and 26th, as shown above.

    Venus (magnitude –4.8) is the brilliant "Evening Star" in the southwest during dusk, shining about as high and bright as it's going to this year. It sets more than an hour after dark. In a telescope, Venus has waned to its thick-crescent phase and has enlarged to about 34 arcseconds tall.

    Mars (magnitude 1.3, below the hind feet of Leo) rises around 1 a.m. By dawn it's high in the southeast. In a telescope Mars is still tiny, 5.5 arcseconds wide.

    Jupiter (magnitude –2.5, in Gemini) rises in the east-northeast around 8 p.m., with Pollux and Castor to its left. It blazes highest around 3 a.m. In a telescope Jupiter has grown to 44 arcseconds wide, as it heads toward its January 5th opposition.

    Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are high in the southern sky in early evening. 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 Standard Time (EST) is Universal Time (UT, UTC, or GMT) minus 5 hours.


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