Friday, July 4
Out to watch fireworks? As you're waiting for twilight to end, spot the Moon in the west-southwest with Mars and Spica off to its left, as shown for July 4 here. High above them all shines brighter Arcturus. Saturn is farther left (off the left edge of this illustration). Point them out to your family!
Ceres and Vesta at their closest. The two leading asteroids, currently magnitudes 8.5 and 7.2, appear closest together this evening and tomorrow evening, just 10 arcminutes apart. 1 Ceres is the largest asteroid, and 4 Vesta sometimes becomes the brightest. See our article with finder charts: Super-Close Pairing of Ceres and Vesta.
Saturday, July 5
First-quarter Moon. The half-lit Moon is quite close to Mars as seen from North America. The Moon occults (hides) Mars during daylight for Hawaii and at dusk or night in parts of Latin America; map and timetables.
Sunday, July 6
The Moon this evening poses midway between Saturn at its left and the Mars-Spica pair at its right.
The Moon is very much in the foreground, just 1.3 light-seconds from Earth. Mars is currently 8½ light-minutes away, Saturn is 78 light-minutes away, and Spica is 250 light-years in the background.
Monday, July 7
Now the waxing gibbous Moon shines closely under Saturn in the evening (for North America), as shown at right. For southern South America, the Moon occults Saturn; map and timetables.
Tuesday, July 8
The Moon's latest daily shift eastward brings it left of Saturn and upper right of Antares at nightfall. Closer below the Moon are Beta and Delta Scorpii (as seen from North America).
Wednesday, July 9
Can your scope separate a double star 1.0 arcsecond wide? High overhead, 44 Bootis provides a fine test. And one of its components is a weird variable star. See the article and chart in the July Sky & Telescope, page 52.
Thursday, July 10
Vega is the brightest star very high in the east these evenings. The brightest to its lower left is Deneb. Farther to Vega's lower right is Altair. These make up the big Summer Triangle.
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 evening 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.
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 to the lower left of Venus. The gap between them diminishes every morning. Mercury is faint but brightening: from magnitude +1.5 to +0.2 this week. Binoculars help.
Venus (magnitude –3.9, In Taurus) shines low in the east during dawn. Look for Aldebaran (much fainter) to Venus's right early in the week, and upper right of it later in the week.
Mars (magnitude +0.1, in Virgo) is high in the southwest at dusk with Spica, a little fainter, closing in on it each day. On July 4th they're 4.5° apart. They'll pass each other 1.3° apart on July 13th. In a telescope Mars's gibbous disk is 9 arcseconds tall, and it continues to shrink.
Jupiter is lost in the sunset.
Saturn (magnitude +0.4, in Libra) glows highest in the south in late twilight. The wide binocular double star Alpha Librae glimmers to its lower right. Antares and the head of Scorpius are farther to Saturn's lower left.
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.