In August, the most beautiful scenery and impressive celestial events are to be enjoyed before dawn—along with much more comfortable temperatures for sky watching.
At least three of the five bright planets, plus at least nine stars of first-magnitude or brighter, are all simultaneously visible before dawn. By Aug. 14, the Dog Star Sirius, the brightest star—ranking next in brilliance after Venus and Jupiter—rises in twilight in the east-southeast. Find it by extending the three-star belt of Orion down toward the horizon. Rising left of Sirius, a few degrees north of due east and, for the Coachella Valley, about 6 minutes earlier, is Procyon, the ”before the Dog” star, announcing the imminent rising of Sirius. The planet Mercury, to the lower left of Venus, appears above the eastern horizon, bringing the total to four bright planets and 11 bright stars.
Here are additional rewards for early risers:
On Tuesday, Aug. 12, a close pairing of the two brightest planets, Venus and Jupiter, just 0.9° apart, is the most impressive planetary conjunction of this year, with the 88 percent waning gibbous moon appearing close to Saturn that same morning.
Also on Aug. 12, and on the 13th, in predawn darkness hours, the Perseid meteor shower is near its peak.
On Aug. 16, the moon, 47 percent lit, is nearly half-full and just past last quarter phase, near the Pleiades star cluster, making a wonderful field for binoculars. On Aug. 17, a 36 percent crescent moon is widely north of Aldebaran and the Hyades star cluster. The “V” formation of Aldebaran and the Hyades makes up the head of Taurus, and fits nicely into the field of view of binoculars.
On Aug. 19, a 16 percent crescent moon appears near Jupiter. On Aug. 20, a thinner 9 percent moon, with earthshine visible on its darker, non-sunlit side, appears near Venus and the Twin stars Pollux and Castor. And on Aug. 21, a thin 4 percent crescent moon appears near Mercury.
Mercury, after passing inferior conjunction nearly between Earth and the sun on July 31, enters the morning sky. Deep in bright twilight at first, it attains first magnitude by Aug. 14, when it can be spotted very low in the east-northeast an hour before sunrise, 18° to the lower left of Venus. It gets better! Mercury brightens to magnitude zero by Aug. 18, when it’s 16° to Venus’ lower left. Mercury climbs highest in twilight and approaches closest to the lower left of Venus, by 15°, on Aug. 20-21. Continuing to brighten as it heads toward the far side of the sun, Mercury reaches magnitude 1.0 on Aug. 27, while dropping lower, to 17° to the lower left of Venus. By Aug. 31, Mercury shines at magnitude -1.2, but is still lower in twilight, 19° to the lower left of Venus. Mercury will pass superior conjunction, hiding on far side of sun, on Sept. 13.
The faint distant ice giant planets, 5.7-magnitude Uranus and 7.8-magnitude Neptune, can be viewed with optical aid before morning twilight begins. Uranus is easy for binoculars, within 4.4° to the south of third-magnitude Alcyone, the Pleiades’ brightest star. Neptune is 1.1° north to 1.7° north-northeast of Saturn this month, so a small shift in the aim of the telescope after you inspect Saturn’s rings will bring the faint planet into view. Change to a high power eyepiece to discern the tiny round disks of Uranus and Neptune, distinguishing them from background stars.
That makes a total of six planets visible in the August morning sky, after Mercury has become easy to see around mid-month. The six planets, in order from east to west, are Mercury, Venus, Jupiter, faint Uranus, faint Neptune and Saturn. They span 124° on Aug. 15; 130°on Aug. 21; 135° on Aug. 25; and 146°on Aug. 31. Over a span of 10 mornings, August 12-21, the waning moon passes eastward along the planetary lineup, from Saturn to Mercury, and the much more distant background stars of the zodiac constellations Pisces, Aries, Taurus, Gemini and Cancer.
In the evening sky about an hour after sunset on Aug. 1, golden Arcturus, high in the west-southwest, and blue-white Vega, high in the east-northeast, are the brightest stars visible. Altair and Deneb complete the Summer Triangle with Vega. The moon, 56 percent full and just past first quarter phase, is in Libra, midway between blue-white Spica in the southwest, and reddish Antares in south, 23° from each. Mars, dim at magnitude +1.6, is low in the western sky, 27° to the lower right of Spica. It’s no coincidence that Mars, Spica, the moon and Antares lie in a nearly straight line, since Spica and Antares lie only a few degrees south of the ecliptic (plane of Earth orbit), within 2.1° and 4.6°, respectively.
Watch the moon shift position eastward by an average of 13.2° daily, returning to the same stars after 27.3 days. On the evening of Aug. 2, the 65 percent moon is 11° to the west of Antares. On Aug. 3, the 74 percent moon appears 1°-2° to the lower left of Antares one hour after sunset. On Aug. 4, the southernmost, 82 percent moon appears in Ophiuchus, the Serpent-bearer, 13° to the lower left of Antares. Notice how unusually low the moon is as it passes directly south that night, only 27° up for the Coachella Valley, 1.6 hours after sunset, nearly 6° lower than the Dec. 21 winter solstice midday sun. Later that night, watch the moon set unusually far south of west, [4.8 hours after reaching its high point for the Coachella Valley.
On the evening of Aug. 5, the 89 percent moon appears within the Teapot, an eight-star asterism within the constellation Sagittarius, the Archer. On the next evening, the 95 percent moon is east of the Teapot.
The moon is full on the night of Aug. 8-9, rising around sunset and setting shortly after sunrise. Thereafter, watch the waning gibbous moon rise farther north and not much later each successive evening, but still before the end of twilight. On the evening of Aug. 11, about two hours after sunset, watch for Saturn rising within 5° to the lower left of the 90 percent moon. The 88 percent moon and Saturn appear closest the next morning, Aug. 12, about 3° apart, high in the southern sky, 1 1/2 hours before sunrise. The best dates for viewing the Milky Way, high in the sky with little or no moonlight at the end of evening twilight, are Aug. 13-26.
The moon returns to the evening sky on Aug. 24, as a 4 percent crescent, very low in the west in bright twilight, a half-hour after sunset.
On Aug. 25, 40 minutes after sunset, the 8 percent crescent is very low, south of west. Try for faint Mars (magnitude +1.6) within 7° to the upper left of the moon, and 12° to the lower right of first-magnitude Spica.
On Aug. 26, the 16 percent crescent is low in the west-southwest, with Mars within 7° to its right, and Spica 6° to the moon’s upper left.
On Aug. 27, one hour after sunset, the 22 percent crescent is low in the west-southwest, with Spica within 7° to the right, and Mars 11° to the lower right of Spica.
One hour after sunset on Aug. 28, the 30 percent crescent moon in the southwest has Spica 18° to its lower right, and Antares 28° to its upper left. At the same stage of twilight on Aug. 29, the 39 percent moon is 17° to the lower right of Antares.
On Aug. 30, one hour after sunset, the 49% moon, nearing first quarter phase, is in the south-southwest, 4° to the lower right of Antares.
On Aug. 31, one hour after sunset, the 58 percent, slightly gibbous moon is in the south to south-southwest, 8° to the lower left of Antares. Mars ends August to the 8.5° lower right of Spica.
Tomorrow night, Spaceship Earth, in its orbit around the sun, will be carrying us toward a direction 5° north of Aldebaran in the morning sky, and racing away from a direction 5° north of Antares in the evening sky.
The Astronomical Society of the Desert will host a star party on Saturday, Aug. 23, at Sawmill Trailhead, a site in the Santa Rosa Mountains at elevation 4,000 feet; and on Saturday, Aug. 30, at the Santa Rosa and San Jacinto Mountains National Monument Visitor Center. For more information, including maps and directions to the two observing sites, visit astrorx.org.
Robert Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 and still helps produce an occasional issue. He enjoys being outdoors sharing the beauty of the night sky and other wonders of nature. Robert Miller, who provided the evening and morning 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.
