Friday, July 11
Mars and Spica form a striking pair in the southwestern sky at dusk! They're now just under 2° apart. On Sunday evening they'll be at their minimum separation, 1.3°. Watch them change day by day.
Full Moon tonight and Saturday night (exactly full at 7:25 a.m. Saturday morning Eastern Daylight Time.) This evening the Moon shines in northern Sagittarius. Tomorrow it's in western Capricornus.
Saturday, July 12
Look far above the still-full Moon this evening, and a bit left, to spot Altair. Continue a similar distance in roughly the same direction, and there's brighter Vega.
Sunday, July 13
This is the evening when Mars shines closest to Spica. Look southwest at nightfall. They're 1.3° apart. Fiery Mars is the brighter one.
Monday, July 14
The tail of Scorpius is low in the south after dark — how low depends on how far north you are. Look for the two stars especially close together in the tail. These are Lambda and fainter Upsilon Scorpii, Shaula and Lesath, known as the Cat's Eyes. They're canted at an angle.
They point west by nearly a fist-width toward Mu Scorpii, a much tighter pair known as the Little Cat's Eyes. Can you resolve Mu without using binoculars?
Tuesday, July 15
Vega is the brightest star very high in the east. Far down to its lower right shines Altair, almost as bright. Look left of Altair by about a fist and a half at arm's length, and a little lower, for dim, compact Delphinus, the Dolphin. It's leaping in the lower edge of the Milky Way.
Wednesday, July 16
If you have a dark enough sky, the Milky Way now forms a magnificent arch high across the whole eastern sky after nightfall is complete. It runs all the way from below Cassiopeia in the north-northeast, up and across Cygnus and the Summer Triangle in the east, and down past the spout of the Sagittarius Teapot in the south.
Thursday, July 17
The Big Dipper, high in the northwest after dark, is beginning to turning around to "scoop up water" through the nights of summer and early fall.
The waning Moon, nearly at last quarter, rises around 11 or midnight and climbs high in the early-morning hours. Far in its background is Uranus, magnitude 5.8. Locate it with binoculars or a wide-field telescope and our finder chart for Uranus among the stars.
Friday, July 18
Last-quarter Moon (exact at 10:08 p.m. Eastern Daylight Time). The Moon rises around midnight tonight, shining in Pisces.
Early Saturday morning before dawn, the faint asteroid 611 Valeria will occult an 8.7-magnitude star in Pisces for observers along a track crossing northern Mexico, Texas, the Deep South (including the Atlanta area) and the Carolinas. Details, times, finder chart.
Saturday, July 19
Mars is still slightly less than 3° (two finger widths at arm's length) from Spica, but they're sinking lower in the southwest at dusk.
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.
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 fairly heavy and expensive). 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
Mercury is low in the glow of sunrise, just 7° lower left of brilliant Venus all week. Mercury brightens from magnitude +0.4 to –0.4 this week.
Venus (magnitude –3.8) shines low in the east-northeast during dawn. You'll find Mercury to its lower left, Aldebaran increasingly far to its upper right, and Capella far to its upper left.
Mars (magnitude +0.2, in Virgo) is high in the southwest at dusk — with Spica right by it! They pass each other 1.3° apart on July 13th, then their separation gradually widens. In a telescope, Mars's gibbous disk is only about 8.7 arcseconds tall and shrinking.
Jupiter is hidden deep in the sunset.
Saturn (magnitude +0.4, in Libra) glows highest in twilight in the south-southwest. It's off to the left or upper left of the Mars-Spica pair. After dark, look for fainter Alpha Librae lower right of Saturn, and Beta Librae about twice as far above Saturn.
In a telescope Saturn's globe is 18 arcseconds wide, and its rings are tilted 21° from our line of sight. Use our SaturnMoons app to find and identify Saturn's satellites at any time and date. A 6-inch scope will show four or five of them: Titan, Rhea, Dione, Tethys, and sometimes Iapetus.
Uranus, in Pisces, and Neptune, in Aquarius, are well up in the southeast and south before the first light of dawn. Use our 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 Daylight Time (EDT) is Universal Time (UT, UTC, or GMT) minus 4 hours.