Friday, September 2
• Neptune reaches opposition and peak visibility today. Because it lies opposite the Sun in our sky, it rises at sunset and appears highest in the south around 1 a.m. local daylight time. But you can start searching for it by 10 p.m., when it lies nearly one-third of the way from the southeastern horizon to the zenith. Neptune glows at magnitude 7.8, bright enough to spot through binoculars if you know where to look. The trick is to find the 4th-magnitude star Lambda (l) Aquarii, which lies about 10° southeast of Aquarius’ distinctive Water Jar asterism. At opposition, Neptune appears 1.3° southwest of this star. When viewed through a telescope, Neptune shows a blue-gray disk measuring 2.4″ across.
Saturday, September 3
• Look to the western sky shortly after sunset this evening and you’ll see a beautiful alignment of the Moon with Venus and Jupiter. Our satellite, which reached its New phase just two days ago, now appears 7 percent lit and stands highest. The three objects form a straight line spanning some 14°, with Venus midway between the other two. Venus shines at magnitude –3.8, some two magnitudes brighter than its planetary cousin. Although Jupiter disappears in the twilight glow later this week, Venus spends the next several months climbing higher and growing more conspicuous.
Sunday, September 4
• The Moon’s absence from the morning sky these next ten days provides observers with an excellent opportunity to see the zodiacal light. From the Northern Hemisphere, the time around the autumnal equinox is the best for viewing the elusive glow before sunrise. It appears slightly fainter than the Milky Way, so you’ll need a clear moonless sky and an observing site located far from the city. Look for a cone-shaped glow that points nearly straight up from the eastern horizon shortly before morning twilight begins (around 5 a.m. local daylight time at mid-northern latitudes). The Moon remains out of the morning sky until September 14, when the waxing gibbous returns and overwhelms the much fainter zodiacal light.
Monday, September 5
• The constellations Ursa Major the Great Bear and Cassiopeia the Queen lie on opposite sides of the North Celestial Pole, so they pivot around the North Star (Polaris) throughout the course of the night and the year. In late August and early September, these two constellations appear equally high as darkness falls. You can find Ursa Major and its prominent asterism, the Big Dipper, about 30° above the northwestern horizon. Cassiopeia’s familiar W-shape, which currently lies on its side, appears the same height above the northeastern horizon. As the night progresses, Cassiopeia climbs above Polaris while the Big Dipper swings below it.
Tuesday, September 6
• Distant Uranus has finally become a nice target for evening observers. The ice giant planet rises around 9 p.m. local daylight time and climbs some 25° above the eastern horizon by 11 p.m. The magnitude 5.7 planet lies in Pisces, 2.5° north of magnitude 4.8 Mu (m) Piscium. Although Uranus glows bright enough to see with the naked eye under a dark sky, binoculars make the task much easier. A telescope reveals the planet’s blue-green disk, which spans 3.7″.
• The Moon reaches apogee, the farthest point in its orbit around Earth, at 2:45 p.m. EDT. It then lies 251,689 miles (405,055 kilometers) from Earth’s center.
Wednesday, September 7
• Evenings this week are great times for exploring the constellation Sagittarius the Archer. This star group lies due south and at peak altitude around 9 p.m. local daylight time, just as the last vestiges of twilight fade away. The brightest stars within the constellation form the shape of a teapot — a distinctive asterism once you’ve found it. The central regions of the Milky Way pass through Sagittarius, so it’s always worth exploring the area through binoculars or a telescope.
Thursday, September 8
• The nearly First Quarter Moon appears 4° above Saturn this evening. The pair stands about 20° high in the southwest as darkness falls. Although the duo looks best with the naked eye and binoculars, don’t pass on the opportunity to view Saturn through a telescope. The magnitude 0.5 planet measures 16″ across while its dramatic ring system spans 37″ and tilts 26° to our line of sight. As a bonus, the ringed planet reached quadrature only six days ago, so a line from the Sun to Earth and then to Saturn formed a right angle. Observationally, this means that Saturn’s shadow now extends farthest east of the planet and shows up plainly on the rings, giving the world a striking 3-D appearance.
• Although September is typically a slow month for meteors, the International Meteor Organization has identified a relatively new shower called the Epsilon Perseids. Observers witnessed an unexpected flurry of “shooting stars” radiating from the constellation Perseus in both 2008 and 2013. In other years, the rate topped out at five meteors per hour. In 2016, the shower peaks late this evening, though the best views will come after midnight once the Moon has set and Perseus rides high in the sky.
Friday, September 9
• First Quarter Moon arrives at 7:49 a.m. EDT. Our satellite won’t rise until around 2 p.m. local daylight time, however, so observers in the Americas won’t see it precisely half-lit. As darkness falls tonight, the Moon appears about 55 percent lit and lies nearly 10° above Mars. The Red Planet is worth exploring in detail any night this week. It shines at magnitude –0.2 and shows a 10″-diameter, orange-red disk with several subtle dark markings when viewed through a telescope.
Saturday, September 10
• If you look overhead as darkness falls anytime this week, your eyes will fall on the brilliant star Vega in the constellation Lyra the Harp. At magnitude 0.0, Vega is the brightest member of the prominent Summer Triangle asterism. The Triangle’s second-brightest star, magnitude 0.8 Altair in Aquila the Eagle, lies some 35° southeast of Vega. The asterism’s dimmest member, magnitude 1.3 Deneb in Cygnus the Swan, stands about 25° east-northeast of Vega. Deneb trails Vega by about two hours and passes through the zenith at approximately 10:30 p.m. local daylight time.
Sunday, September 11
• Asteroid 2 Pallas reached opposition and peak visibility three weeks ago, but it remains a tempting target in the evening sky. The second-largest object orbiting between Mars and Jupiter glows at magnitude 9.4, bright enough to show up through almost any telescope. You can find it in the dim constellation Equuleus the Little Horse, which lies just west of its big cousin, Pegasus. This evening, the asteroid lies 1° due west of Equuleus’ brightest star, magnitude 3.9 Alpha (a) Equulei. The two objects climb nearly two-thirds of the way to the zenith in the southern sky around 11 p.m. local daylight time
