FRIDAY, MARCH 31
■ There comes a time now in late evening when Arcturus, the bright Spring Star climbing in the east, stands just as high as Sirius, the brighter Winter Star descending in the southwest. Their heights will exactly balance sometime around 10 or 11 p.m. daylight-saving time, depending on both your latitude and your longitude.
These are the two brightest stars in the sky at the time. But Capella is a very close runner-up to Arcturus! Spot it high in the northwest.
■ Capella's pale-yellow color matches that of the Sun, meaning they're both about the same temperature. But otherwise Capella is very different. It consists of two yellow giant stars orbiting each other every 104 days.
Moreover, for telescope users, it's accompanied by a distant, tight pair of red dwarfs: Capella H and L, magnitudes 10 and 13. Article and finder charts.
SATURDAY, APRIL 1
■ The waxing gibbous Moon shines in Leo, again forming an isosceles triangle with Regulus below it (in early evening) and Gamma Leonis (Algieba) to the Moon's left. The Moon is about 6° from each star.
SUNDAY, APRIL 2
■ Now the Moon forms a different nearly isosceles triangle with Regulus and Algieba. This time it's to their lower left and farther away from them.
■ The huge, bright Winter Hexagon is still in view early after dark, filling the sky to the southwest and west. It's the biggest widely-recognized asterism.
Start with brilliant Sirius in the southwest, the Hexagon's lower left corner. High above Sirius is Procyon. From there look higher upper right for Pollux and Castor (lined up nearly horizontal), lower right from Castor to dim Beta Aurigae and then bright Capella, lower left from there to Aldebaran, lower left to Rigel at the bottom of Orion, and back to Sirius.
The Hexagon is somewhat distended. But if you draw a line through its middle from Capella to Sirius, the "Hexagon" is fairly symmetric with respect to that axis.
MONDAY, APRIL 3
■ Right after dark, Orion is still well up in the southwest in his spring orientation: striding down toward the right, with his belt horizontal.
The belt points left toward Sirius and right toward Aldebaran and, farther on, the Pleiades.
TUESDAY, APRIL 4
■ At this time of year, the two Dog Stars stand vertically aligned around the end of twilight. Look southwest. Brilliant Sirius in Canis Major is below, and Procyon in Canis Minor is high above.
WEDNESDAY, APRIL 5
■ Full Moon tonight (exact at 12:35 a.m. EDT). After dark, look for Spica below it and brighter Arcturus several times farther to the Moon's left.
THURSDAY, APRIL 6
■ The Moon, a day past full, rises in late twilight with Spica about 4° or 5° to its upper right. They cross the sky together through the night, slowly drawing farther apart.
Spot Arcturus three fists to their upper left during evening.
FRIDAY, APRIL 7
■ By now Mercury is in easy view in late twilight, far to the lower right of Venus as indicated in the scene below. And once the sky is dark enough, spot the Pleiades above Venus.
■ Vega, the bright "Summer Star," rises in the northeast late these evenings. Exactly where should you watch for it to come up? Spot the Big Dipper almost overhead in the northeast. Look at Mizar at the bend of its handle. If you can see Mizar's tiny, close companion Alcor (binoculars show it easily), follow a line from Mizar through Alcor all the way down to the horizon. That's where Vega will make its appearance.
SATURDAY, APRIL 8
■ Castor and Pollux shine together high in the west-southwest after dark. Pollux, on the left, is slightly the brighter of these "twins."
Draw a line from Castor through Pollux, follow it farther left by a big 26° (about 2½ fist-widths at arm's length), and you're at the dim head of Hydra, the Sea Serpent. In a dark sky Hydra's head is a subtle but distinctive star grouping, about the width of your thumb at arm's length. Binoculars show its stars easily through light pollution.
Continue the line farther by a fist and a half and you hit Alphard, Hydra's 2nd-magnitude orange heart.
Another way to find the head of Hydra: It's almost midway from Procyon to Regulus.
SUNDAY, APRIL 9
■ The waning gibbous Moon rises around midnight tonight, closely accompanied by orange Antares. By the time dawn begins Monday morning, they're well up in the south.
This Week's Planet Roundup
Mercury shows itself a little higher in the afterglow of sunset day by day, above the west horizon. Look for it starting about a half hour after sunset, far to the lower right of bright Venus. Binoculars may help.
But even as Mercury gains altitude this week its brightness fades in half, from magnitude –1.1 on Friday March 31st to –0.4 on Friday April 7th.
Venus (magnitude –4.0, crossing from Aries into Taurus) is the brilliant "Evening Star" shining in the west during and after dusk. It doesn't set until almost 2 hours after dark. Telescopically, Venus is a shimmering little gibbous ball 14 arcseconds in diameter and about 76% sunlit.
Mars is cruising eastward above the trailing foot of the Castor stick-figure in Gemini. Look for it high in the west in early evening, lower in the west later. It's upper left of Venus by about four fists at arm's length.
Mars continues to fade: from magnitude +1.0 to +1.1 this week. It looks similar to Mars-colored Aldebaran (+0.9) some 25° below it, and Mars-colored Betelgeuse (currently +0.4) in Orion's shoulder a little less far to Mars's lower left. These form the big, temporary Orange Triangle, which continues to change shape. It's connected to the larger, brighter Winter Triangle at its Betelgeuse corner.
Mars is nearly on the other side of its orbit from us, so in a telescope it's just a little orange blob 6 arcseconds wide.
Jupiter is out of sight, nearly behind the Sun.
Saturn, magnitude +1.0 in Aquarius, is emerging into dawn view, very low in the east-southeast as the sky brightens. Again, binoculars help. Look for it far, far below Altair.
Uranus, magnitude 5.8 in Aries, is now a more difficult binocular catch as it sinks in the west below Venus.
Neptune, mag 8.0, is still hidden in the sunrise.
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 sometimes called 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.
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 magnitude 9.75). And be sure to 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 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. 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
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