This Week’s Sky at a Glance, April 1 – 9

Jupiter under Leo, early April 2016

All this week, Leo shines over Jupiter in the evening sky.

Mars, Saturn, and Antares at dawn, early April 2016

All week, Saturn, brighter Mars, and fainter Antares form a shifting triangle in the south before dawn. These scenes are drawn for latitude 40° north (for instance New York, Denver, Madrid). If you're south of there, things in the southern sky will appear higher than shown; north of there, lower. The blue 10° scale is about the width of your fist held at arm's length.

Friday, April 1

• Spring is here! Which means Arcturus shines brightly in the east, though still not high. The Big Dipper, high in the northeast, points its curving handle to the lower right down toward it. Jupiter shines very high far to Arcturus's upper right.

Arcturus forms the pointy end of a long, narrow kite pattern formed by the brightest stars of Bootes, the Cowherd. The kite is currently lying on its side to Arcturus's left. The head of the kite, at the far left, is bent slightly upward. The kite is 23° long, about two fist-widths at arm's length.

• This evening, telescope users along a narrow path from the Seattle/Vancouver area to Arkansas can watch for a 9.5-magnitude star (located 10° northwest of the Pleiades) to disappear for up to 9 seconds behind the invisibly faint asteroid 2892 Filipenko. Track map and finder charts for the shadow path across the US, the star to be occulted, and times.

Saturday, April 2

• This is the time of year when Arcturus shines just as high in the east as Sirius, the brighter Winter Star, shines in the southwest (as seen from mid-northern latitudes).

Sunday, April 3

• Draw a line from Castor through Pollux and follow it farther out by a big 26° (about 2½ fist-widths at arm's length). You're at the dim head of Hydra, the Sea Serpent. In a dark sky it's a subtle but distinctive asterism about the size of your thumb at arm's length. Through light pollution, binoculars show it easily.

Monday, April 4

Double shadow on Jupiter late tonight, for telescope users in central and western North America. From 2:37 to 3:19 a.m. Tuesday morning Pacific Daylight Time, both Io and Europa cast their little shadows onto the planet.

Tuesday, April 5

• The huge, bright Winter Hexagon is still in good view at nightfall, filling the sky to the southwest and west. Start with brilliant Sirius in the southwest, the Hexagon's lower left corner. High above Sirius is Procyon. From there look even higher for Pollux and Castor, lower right from Castor to Menkalinen and bright Capella, lower left to Aldebaran, lower left to Rigel at the bottom of Orion, and back to Sirius.

Wednesday, April 6

• Io crosses the face of Jupiter tonight from 9:52 p.m. to 12:07 a.m. EDT, followed by its more visible black shadow from 10:32 p.m. to 12:47 a.m. EDT.

Meanwhile, Europa disappears behind Jupiter's preceding (celestial western) limb at 10:48 p.m. EDT.

Moon and Mercury at dusk, April 8-10, 2016

As Mercury emerges into its best evening apparition of 2016, the crescent Moon guides your way down to it.

Thursday, April 7

• Io emerges from eclipse by Jupiter's shadow, just beyond Jupiter's following limb, at 10:04 p.m. EDT.

• New Moon (exact at 7:24 a.m. EDT).

Friday, April 8

• Looking west in twilight, use the thin crescent Moon as your guidepost to Mercury, as shown at right.

• Jupiter this evening is just 0.1° north of 5th-magnitude Chi Leonis. Binoculars show the star looking like an out-of-place moon of Jupiter. A 6-inch telescope may show that, compared to this star, Jupiter's moons are not quite pinpoints.

Saturday, April 9

• The crescent Moon shines in the west in twilight. Look for Mercury far down to its lower right, as shown here. Then as the stars come out, spot Aldebaran to the Moon's upper left and the Pleiades to its upper right.
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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 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.

Pocket Sky Atlas, jumbo edition

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae. Shown above is the new Jumbo Edition for easier reading in the night. Click image for larger view.

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 new 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, is the even larger 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 Sue French's Deep-Sky Wonders collection (which includes its own charts), 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."


This Week's Planet Roundup

Mars showing Hellas and Syrtis Major, March 23, 2016

Mars on March 23rd, imaged by Christopher Go with a 14-inch scope. South is up. The big white patch at top is not the South Polar Cap or South Polar Cloud Hood but the Hellas basin, which often fills with clouds or frost. The now-small North Polar cap is at bottom. The big dark peninsula at center is Syrtis Major; Hellas is due south of this landmark. Extending to the right-hand limb (celestial east; following ) is thinner Sinus Sabaeus ending with Sinus Meridiani. The dark arc just inside the entire bright limb is a processing artifact. Watch out for these "echoing" bright/dark borders in planetary images.

Jupiter with Great Red Spot on meridian, Mar. 5, 2016

Jupiter's Great Red Spot is still strikingly red. Christopher Go took this image at 16:45 March 5th UT, just a few minutes before the spot reached the central meridian. South is up. Notice the smooth vs. turbulent difference in the South Equatorial Belt preceding (left) and following the Red Spot.

Mercury (bright at magnitude –1.5 to –1.0) emerges into evening view this week. Look for it low in the west-southwest in bright twilight. Binoculars will help. By late in the week it will be easy naked-eye. Mercury is coming into its best evening apparition of the year.

Venus is deep in the glow of sunrise. Can you still make it out at all? Bring binoculars, and look barely above the horizon due east as dawn grows very bright. This the end of the long morning apparition of Venus that began last summer.

Mars (about magnitude –0.5, at the head of Scorpius), rises around midnight daylight-saving time. Before dawn it blazes yellow-orange in the south, to the right of dimmer Saturn. In a telescope Mars is about 12 arcseconds in diameter — quite big enough now to show surface features in a good 3-inch scope at high power during good seeing.

By the time of its opposition and closest approach in late May, Mars will quadruple in brightness and grow to 18.6 arcseconds wide. See our telescopic guide to Mars in the April Sky & Telescope, page 48.

Jupiter (magnitude –2.4, near the hind foot of Leo) shines high in the southeast after dusk and highest in the south by 11 or midnight. It sets in the west before sunrise. See our telescopic guide to Jupiter in the March Sky & Telescope, page 48.

Saturn (magnitude +0.4, in the legs of Ophiuchus) rises around midnight or a bit later, 10° lower left of Mars. By early dawn they stand in the south — Saturn on the left, bright Mars on the right — with fainter, Mars-colored Antares below them making it a triangle.

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

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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 that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time (UT, UTC, or GMT) minus 4 hours.

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“This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours.”

— Neil deGrasse Tyson