This Week's Sky at a Glance, April 17 – 25

Friday, April 17

■ Venus this week continues to blaze as the "Evening Star" in the west during and after twilight. This evening it's passing 10° north (upper right) of Aldebaran, as shown below. And catch the Pleiades lower down.

That V-shaped pattern including Aldebaran? Those other stars are the brightest of the huge, sprawling Hyades cluster. The brightest of them, Theta Tauri (2° under Aldebaran), is a wide double star. Can you resolve it with your unaided eyes? Binoculars make it easy. Theta-1 and Theta-2 are a tenth of a degree apart.

■ Right after dark this week, Orion is still in the southwest in his spring orientation: striding down to the right, with his three-star belt nearly horizontal (depending on your latitude). The belt points left toward Sirius and right toward Aldebaran (and, upper right of Aldebaran, brilliant Venus). See Gary Seronik's A Farewell to Orion.

Orion's uppermost bright star is orange Betelgeuse. It's now fully back to normal at magnitude +0.4, after taking an unusual dip in brightness last winter that bottomed out at magnitude +1.6 in February. Didn't go supernova, did it? We told ya!

Saturday, April 18

■ This is the time of year when, as the last of twilight fades away, the dim Little Dipper extends straight to the right from Polaris. High above the end-stars of the Little Dipper's bowl, you'll find the end-stars of the Big Dipper's bowl.

Sunday, April 19

■ Arcturus is the brightest star in the east these evenings. Spica shines lower right of it by about three fists at arm's length. To the right of Spica by half that distance, look for the distinctive four-star constellation Corvus, the springtime Crow.

Monday, April 20

■ With the evening sky moonless, do an explore of the dim constellation Sextans, south of Regulus, using your telescope and the Deep-Sky Wonders column, chart, and drawings in the April Sky & Telescope, page 54. The brightest of Sextans' deep-sky objects is the edge-on lenticular galaxy NGC 3115. At 9th magnitude, it's a fairly easy catch in a 4- or 6-inch telescope under a good sky — if you know how to use a chart with your telescope!

And at low power with a wide field of view, can you catch Rinnan's Run? It's a remarkably straight "star chain" of 8th- and 9th-magnitude stars, 2.3° long and detectable with large binoculars in a good dark sky.

Tuesday, April 21

■ This evening and tomorrow evening, Venus is crossing the line from Aldebaran at its lower left to Capella twice as far to its upper right.

■  The Lyrid meteor shower, somewhat unpredictable, ought to be active in the early-morning hours of Wednesday and Thursday. The shower's predicted peak falls midway between those two mornings for North America. But at least the sky will be moonless. Under excellent dark-sky conditions shortly before dawn, you might see up to 10 meteors per hour. . . or not.

Wednesday, April 22

■  Bright Arcturus is climbing high in the east these evenings. Equally bright Capella is descending high in the northwest, to the upper right of Venus. Arcturus and Capella stand at exactly the same height above your horizon at some moment between about 8:30 and 10:00 p.m. daylight-saving time, depending mostly on how far east or west you live in your time zone.

■ Arcturus is the brightest star of Bootes, the Cowherd. It's the pointy end of the Kite asterism formed by Bootes's brightest stars. The Kite, rather narrow, lies on its side to Arcturus's left. Its head, at the far left, is bent slightly upward. The kite is 23° long: about two fist-widths at arm's length.

■ New Moon (exact at 10:26 p.m. EDT).

Thursday, April 23

■  Right after dark, the Sickle of Leo stands vertically upright high in the south. Its bottom star is Regulus, Leo's brightest. Leo himself is walking horizontally westward. The Sickle forms his front leg, chest, mane, and part of his head.

Friday, April 24

■ As twilight fades, look way down below Venus near the horizon to pick up the thin, two-day-old crescent Moon starting a new lunation, as shown below. Binoculars help in bright twilight, and as the sky darkens they will help show the earthshine on the Moon's nightlands before the Moon sets.

Saturday, April 25

■ The waxing crescent Moon stands with Aldebaran below Venus this evening, as shown above. The earthshine within its horns ("the old moon on the new moon's arms") will now be in much better view than yesterday. The Moon's dark limb will occult Epsilon Tauri in the Hyades, magnitude 3.5, for eastern Canada and the northernmost eastern US.

This Week's Planet Roundup

Mercury is hidden in the glow of sunrise.

Venus (magnitude –4.7, in north-central Taurus) is the dazzling white "Evening Star" in the west during and after dusk. For the next three weeks it will continue to shine as bright as it gets. Look upper right of it for Capella, two fists at arm's length away. Look half that far lower left of Venus for Aldebaran. Venus finally sets in the northwest about 2 hours after twilight's end.

With Venus is at its brightest and still fairly high after the end of twilight, have you ever managed to see your Venus shadow? You'll need a very dark location! See Bob King's Shadow Casting with Venus.

In a telescope, Venus has enlarged to 33 arcseconds in diameter while waning in phase to become a thick crescent 1/3 sunlit. Venus will continue to enlarge and wane, finally becoming a dramatically thin crescent low in twilight in late May as it approaches conjunction with the Sun.

Mars, Jupiter, and Saturn (magnitudes, +0.5, – 2.3, and +0.6, respectively) are lined up in the southeast before and during early dawn.

Jupiter, the brightest, is on the right.

Saturn glows pale yellow 5° to Jupiter's left or lower left.

Mars, farther lower left of Saturn, is moving eastward against the stars away from the other two. On the morning of April 18th Mars is 11° from Saturn; by April 25th it retreats to 16° away.

Uranus and Neptune are hidden behind the glare of the Sun.

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 (UT, UTC, GMT, or Z time) minus 4 hours.

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.

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) and Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger Night Sky Observer's Guide 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 (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.