Venus, Aldebaran, Pleiades in twilight, May 4, 2018
In the west after sunset, Venus stays nearly fixed in place from week to week as seen at the same stage of twilight. But the stars slide down to the lower right. Soon Aldebaran and the Pleiades will be gone. (The blue 10° scale is about the size of your fist held at arm's length.)
Moon, Saturn, Mars at dawn May 4-5-6, 2018
In early dawn, the waning gibbous Moon shines with Saturn and brighter Mars.

Friday, May 4

• Keep a watch on the changing patterns Venus makes with its background stars from week to week. As Aldebaran and the Pleiades sink away, Beta Tauri (El Nath) above Venus closes in.

• Summer is seven weeks off, but the Summer Triangle is making its appearance in the east, one star after another. The first in view is Vega. It's already shining low in the northeast as twilight fades out.

Next up is Deneb, lower left of Vega by two or three fists at arm's length. Deneb takes about an hour to appear after Vega does, depending on your latitude.

The third is Altair, which shows up far to their lower right by midnight.

• As dawn begins on Saturday morning May 5th, the waning gibbous Moon shines between Saturn and Mars, as shown here.

Saturday, May 5

• Jupiter's Great Red Spot crosses the planet's central meridian around 11:56 p.m. Eastern Daylight Time.

• The Eta Aquariid meteor shower should be active before the first light of dawn Sunday morning. It's usually the best shower of the year for the Southern Hemisphere, but northerners have a poorer view of it. Moreover, the light of the waning gibbous Moon will interfere.

• On Sunday morning May 6th the Moon shines with Mars, as shown here.

Sunday, May 6

• Here's a challenge: With Jupiter just two days from opposition, it's currently casting its shadow in space almost exactly away from us. But not precisely so. An eclipse of Io tonight offers a test. At 1:35 a.m. EDT (10:35 p.m. PDT), Io disappears into eclipse by Jupiter's shadow while hanging smack on Jupiter's western (preceding) edge. In your telescope, can you detect that Io fades out just barely off Jupiter's limb rather than behind the limb itself?

Monday, May 7

• Last-quarter Moon tonight (exact at 10:09 p.m. EDT). The Moon rises around 3 a.m. daylight-saving time. By early dawn Tuesday morning, it's far left of Saturn and Mars.

Tuesday, May 8

• Jupiter is at opposition tonight — opposite the Sun as seen from Earth — and about at its closest and brightest for the year. See our telescopic guide to Jupiter in the May Sky & Telescope, page 48.

Wednesday, May 9

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

Far below Arcturus, Jupiter glares.

Thursday, May 10

• These spring nights, the long, dim sea serpent Hydra snakes along level far across the southern sky. Find his head, a rather dim asterism about the width of your thumb at arm's length, in the southwest. (It's lower right of Regulus by about two fists at arm's length. Also, a line from Castor through Pollux points to it about 2½ fists away.) Lower left of this is Hydra's heart, orange Alphard. Hydra's tail stretches all the way to Libra in the southeast. Hydra's star pattern, from forehead to tail-tip, is 95° long.

• In the early-morning hours of Friday, the asteroid 472 Roma should occult a 10.8-magnitude star in Serpens Caput for telescope users along a path from northern California through Georgia. Details and finder charts.

Friday, May 11

• The Arch of Spring spans the western sky in late twilight. Pollux and Castor form its top: they're lined up roughly horizontally in the west-northwest, about three finger-widths at arm's length apart. Look far to their lower left for Procyon, and farther to their lower right for Menkalinan and then bright Capella.

Venus glares below the Arch. Two fists at arm's length left or lower left from Venus, look for Betelgeuse twinkling on its way out.

Saturday, May 12

• Three zero-magnitude stars shine after dark in May: Arcturus very high in the southeast (high above Jupiter), Vega much lower in the northeast, and Capella in the northwest (upper right of Venus). They appear so bright because each is at least 60 times as luminous as the Sun, and because they're all relatively nearby: 37, 25, and 42 light-years from us, respectively.


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, and hundreds of telescopic galaxies, star clusters, and nebulae among them. Shown above is the Jumbo Edition for easier reading in the night. Larger view. Sample chart.

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, 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 on April 28, 2018
Mars on April 28th, imaged by S&T's Sean Walker using the 1-meter Chilescope remotely. South is up. Just above center, dark Sinus Sabaeus runs horizontally with two-pronged Sinus Meridiani on its right (following) end. Near the sunrise terminator (left), dark Syrtis Major is below center. Far above it, Hellas appears only slightly bright.
Jupiter with Great Red Spot on May 1, 2018
Jupiter's Great Red Spot side on May 1st, imaged by Christopher Go. South is up. The dark South and North Equatorial Belts currently appear quite different on this side of the planet, somewhat less so on the other side. Notice the dark rim of the Red Spot Hollow and the massive white turbulence to the spot's following (celestial east) side.
Saturn with new white spot on April 1, 2018
There's a white storm in Saturn's North Polar Region: the elongated white spot near the bottom. But for any chance of detecting it visually, you'll likely need at least a 10- or 12-inch scope with excellent optics during excellent seeing. Damian Peach took this image at at 8:55 April 1st UT using the 1-meter Chilescope.

Mercury (magnitude 0) is having a very low, poor apparition deep in the glow of sunrise. Using binoculars, look for it 15 or 20 minutes before sunrise barely above the east horizon. Nothing else there is as bright.

Venus (magnitude –3.9) shines brightly in the west-northwest during evening twilight and just after. It's nearly as high as it will get all this spring and summer. In a telescope (look early!) Venus is a little disk 12 arcseconds wide and slightly gibbous: 87% sunlit.

Mars and Saturn rise late at night, around 1:30 a.m. and midnight, respectively (daylight-saving time). They're on opposite sides of Sagittarius, shining at magnitudes –0.5 and +0.3, respectively, with Mars on the lower left. Saturn is above the Teapot. By early dawn they're higher in the south.

Their separation widens from 17° on the morning of May 5th (when the Moon shines between them) to 20° on May 12th.

Mars is brightening on its way to an unusually close opposition in late July. Already it's 12 arcseconds wide. What detail can you see on it in your scope? You'll want a Mars map that identifies what features are facing Earth at the time and date you look, such as our free Mars Profiler.

Jupiter (magnitude –2.5, in Libra) is at opposition this week: exactly so on May 8th. It's the brightest point in the sky after Venus sets below the opposite horizon. Jupiter is now as bright and big (44.8 arcseconds across its equator) as it will appear this year.

It's highest in the south, presenting the sharpest views in a telescope, around midnight or 1 a.m. daylight-saving time. By dawn it's very low in the west-southwest.

Uranus is hidden in the glow of dawn.

Neptune is still very low before the beginning of dawn; wait a few more weeks.


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


"Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious."
— Stephen Hawking, 1942–2018


"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


"Objective reality exists. Facts are often determinable. Vaccines save lives. Carbon dioxide warms the globe. Bacteria evolve to thwart antibiotics, because evolution. Science and reason are not a liberal conspiracy. They are how we determine facts. Civilization's survival depends on our ability, and willingness, to do so."
— Alan MacRobert, your Sky at a Glance editor


"Facts are stubborn things."
— John Adams, 1770



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