There are just a half-dozen bright stars visible at dusk this month: The Summer Triangle of Vega, Altair and Deneb (in order of brightness) high in the eastern sky; Arcturus, high in the west-southwest; Spica, in the southwest, to the lower left of Arcturus; and Antares, heart of the Scorpion, in the south.
Mercury hugs the western horizon all month, climbing around midmonth to a maximum altitude at mid-twilight of only 4.6 degrees from the Coachella Valley. Mercury fades slowly, from magnitude -0.5 to +0.3—definitely an unfavorable apparition, despite its greatest elongation of 27 degrees on Aug. 27. Saturn starts August very low in the east-southeast in evening mid-twilight, and shines at magnitude +0.3 all month. Saturn reaches opposition on Aug. 14, visible all night, with the north face of the rings tipped 14 degrees into our view. For a good look at Saturn, just wait until later in the evening, or late in the month, when it’s higher. Jupiter and Mars have both risen by four hours after evening mid-twilight, but they’re much better placed for morning observation.
Waxing moon: On Aug. 3, the 36 percent waxing crescent moon appears 3 degrees to the upper right of Spica at dusk. Although Mercury will be visible, Regulus, at its conjunction 0.8 degrees to the lower left, will be very difficult to see because of bright twilight. On Aug. 6, look for Antares just 4 degrees to the lower left of the 69 percent gibbous moon. On Aug. 11, look for Saturn within 5 degrees to the north (upper left) of the full moon rising in early dusk. They’ll remain about the same distance apart all night.
Do you enjoy watching moonrises? For the next few evenings after the full moon of Aug. 11, the moon comes up farther north nightly, and not much later each night—by much less than the long-term average daily delay of 50 minutes, and sometimes as little as a half-hour from one night to the next. This is an early season preview of the “Harvest Moon Effect.”
Milky Way: By Aug. 17, the moon will be out of the way, allowing an hour or more of dark-sky viewing after twilight ends. Excellent views of the summer Milky Way at its highest in a moonless sky at nightfall continue through Aug. 29, so take the kids to a dark site to enjoy the view of our home galaxy!
Late in month, the moon returns to the evening sky as a crescent in twilight. On the 28th, look for the 3 percent crescent very low in the west, with Mercury 9 degrees to its left and slightly lower. On the 29th, find the 8 percent moon with Mercury 7 degrees to its lower right. And on the 30th, find the 14 percent crescent moon low in the west-southwest, with Spica 4 degrees to its lower left.
Predawn attractions: As August begins, an impressive number of bright objects enhances the sky an hour before sunrise. First is a striking lineup of four planets, 145 degrees long, from brilliant Venus, very low in the east-northeast, through Mars, high in east-southeast, and bright Jupiter, high in south, to Saturn, low in southwest. And these stars: the Summer Triangle of Vega, Deneb and Altair, in the northwest to west; Fomalhaut, mouth of the Southern Fish, to the lower left of Saturn and lower right of Jupiter; Orion with blue Rigel, his foot, low in the east-southeast, and red Betelgeuse, his shoulder, low in the east; Pollux and Castor, twin stars of Gemini, to the left of Venus; Capella, the Mother Goat Star, high above Venus and the Twins; and Aldebaran, eye of Taurus, above Orion and to the lower left of Mars.
By the end of August’s second week, two stars—Procyon, rising in the east, and Sirius, the Dog Star and brightest star, rising in line with Orion’s belt extended down toward the horizon—join the scene. These two stars complete the Winter Triangle with Betelgeuse. Catch it soon, after Sirius rises and before Altair sets, and you’ll see the Summer and Winter Triangles simultaneously! Then 11 of the 16 stars of first magnitude or brighter visible from the Coachella Valley are visible simultaneously.
What distinguished planets from stars for the ancients is that they were “wanderers,” changing their positions against the stars. Watch the changing alignment of Venus with Castor and Pollux on Aug. 10, when the line joining the stars 4.5 degrees apart, extended 8 degrees downward, locates Venus. Watch Mars pass within 6 degrees of the Pleiades star cluster Aug. 17-24.
Beginning with the full moon of Aug. 11, the moon will be added to the lineup of solar system bodies in the morning sky. About one hour before sunrise remains a good time to look. The moon was considered a planet in the ancient, original sense of the word. (And so was the sun, completing a circuit around the zodiac every 12 months.) Watch the waning moon pass the four morning planets.
On Aug. 11, see the nearly full moon about to set, with Saturn 13 degrees above. On the next morning, the full moon will be 5 degrees to the left of Saturn.
The annual Perseid meteor shower reaches peak between nightfall on Friday, Aug. 12, and dawn’s first light on Saturday, Aug. 13. The radiant is highest before first light on Saturday, and that’s when you’d normally expect the greatest number of meteors—but this year’s shower will be spoiled by a full moon occurring on Aug. 11. Look for meteors during the intervals of dark skies from moonset until dawn on the mornings of Aug. 8-10, days before the peak, and from nightfall until moonrise on evenings of Aug. 14-16, after the peak.
On Aug. 14, the 92 percent waning gibbous moon appears 14 degrees to the lower right of Jupiter. The next morning, the 85 percent moon will be 2 degrees to the lower left of Jupiter. This close pairing provides a chance to see Jupiter in the daytime; just keep track of the moon and Jupiter until sunrise! On Aug. 16, the 76 percent moon will appear 14 degrees to Jupiter’s upper left.
On Aug. 17, Mars and Jupiter are 50 degrees apart. The moon, two-thirds full, is high in the south an hour before sunup, and just over halfway from Jupiter toward Mars.
On Aug. 18, using binoculars or a telescope 1 1/2 hours before sunrise, look for the 5.6-magnitude star Rho-3 in Aries, about 1.6 degrees to the upper left of the moon’s center. (The moon is about half a degree in diameter.) Next, catch 5.8-magnitude Uranus about 1.2 degrees to the lower left of the moon’s center and 2.3 degrees to the lower left of Rho-3. Mars is 11 degrees to the east (lower left) of the 57-percent moon.
On Aug. 19, the moon, 47 percent full and just past its last quarter phase, is about 2 degrees from Mars and 3 degrees from the Pleiades, a beautiful field for binoculars! Another gorgeous view awaits 9 to 12 degrees below the moon—Aldebaran and the Hyades star cluster.
On Aug. 20, the 38 percent crescent moon appears 13 degrees to the lower left of Mars, and 7 or 8 degrees to the upper left of Aldebaran. Mornings this weekend, Mars appears 6 or 7 degrees south of the Pleiades star cluster. Today is the middle of three consecutive mornings the moon spends in the constellation Taurus, the Bull.
Can you see the four bright planets simultaneously a little less than an hour before sunrise on Aug. 20? Venus-Mars-Jupiter-Saturn will span nearly 170 degrees, with Venus and Saturn only 5 degrees above opposite horizons.
On Aug. 21, the moon’s final morning in Taurus, the 29 percent crescent lies almost between the tips of the Bull’s horns.
On Aug. 23, look for the “Gemini Twins”—fainter Castor, 4.5 degrees to the upper left of Pollux, some 6 degrees to the lower left of the 13 percent crescent moon. Venus is 26 degrees to the moon’s lower left. On Aug. 24, the Twins are 7 to 11 degrees above the 8 percent crescent, beautifully illuminated by earthshine on its darker side.
On Aug. 25, about an hour before sunrise, find a photogenic 3 percent lunar crescent very low in the east-northeast an hour before sunrise, with Venus 6 degrees to its lower right. If your local landscape prevents you from seeing four bright planets simultaneously, then look earlier to catch Saturn low in the west-southwest, and then later for Venus.
On Aug. 26, 30 minutes before sunrise, find Venus very low in the east-northeast, with a 1 percent crescent moon 8 degrees to its lower left. Binoculars recommended! The moon will be new on Aug. 27 at 1:17 a.m.
Telescopic views: Jupiter, with its dark cloud belts and four bright moons discovered by Galileo, and Saturn, with its rings, are always crowd pleasers. As Mars draws nearer, try to spot Syrtis Major, the first surface feature of another planet ever to be recorded, in 1659. Using a six-inch telescope at 150-200x, observers can note it as a dark triangular marking near the center of the tiny Martian disk on Aug. 15 at 2:24 a.m., and about 40 minutes later on each successive morning for the rest of the week, through Aug. 20, at 5:43 a.m. The south pole is tipped toward the Earth and sun, but summer is advancing, so the polar cap is greatly reduced. Mars’ disk will nearly double in size to 17 arcseconds by closest approach to Earth on Nov. 30.
Faint planets for binoculars: On the mornings of Aug. 1 and 2, just before start of twilight, Uranus, of magnitude 5.8 in Aries, is easy to spot through binoculars, within 1.4 degrees to the upper left of Mars, and 2.1 degrees below 5.6-magnitude Rho-3 (46) Ari. Uranus remains east of a compact isosceles triangle of similarly bright stars Omicron, Sigma and Pi. At the northernmost vertex of the triangle, Pi is 2.4 degrees from Omicron and Sigma, which are 1.7 degrees apart. Uranus itself forms an isosceles triangle with the eastern side of the triangle, Sigma and Pi, 3.6 degrees from each. Mars moves east about 0.6 degrees daily this month, or 18 degrees by month’s end, while Uranus barely moves. It goes only 13 arcminutes, a bit more than 0.2 degrees, by Aug. 24, when it begins retrograde 2.3 degrees east-southeast of Rho-3 Ari, and 3.8 degrees from Sigma and Pi Ari.
Neptune is of magnitude 7.8, near the Aquarius-Pisces border, 13.6 to 12.5 degrees west-southwest of Jupiter in August, and 1.3 to 2.0 degrees west-southwest of 5.5-magnitude 20 in Pisces. This star marks the end of the handle of a compact asterism we’ll call “Neptune’s Dipper,” because it will be useful for locating the planet for the next few years. Comprised of stars of magnitude 4.4 to 5.9 located southeast of the Circlet of Pisces and easy for binoculars, the dipper is marked by the stars 20, 24, 27, 29, 33 and 30 Piscium. Don’t confuse Neptune with the slightly brighter 7.3-magnitude star HIP 117112, just 57 arcminutes (0.95 degrees) west-southwest of 20 Psc.
Sky Calendar includes illustrations of many of the events described in this article. To subscribe or to view a sample issue, visit www.abramsplanetarium.org/skycalendar.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 at Michigan State University, and still produces issues occasionally, including the upcoming October and December 2022 editions. He enjoys being outdoors sharing the wonders of the night sky. Robert Miller, who provided the twilight charts, did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.