Site icon When the Curves Line Up

2018, August: The Evening Planet Parade Begins to Split


August opens with bright Mars in the sky nearly all night, setting about 45 minutes before sunrise.  It is just past its perihelic opposition and closest approach.  Watch Mars dim in brightness and diminish in size as our planet pulls away from its outer neighbor. Mars, the second brightest planet, shines 4° above the southeast horizon during early evening twilight. The other three bright planets – Venus, Jupiter, and Saturn – are farther west. Mercury still has an eastern (evening) elongation, but it sets only 8 minutes after the sun. This speedy planet is headed for its inferior conjunction early in the month.  At Nautical Twilight, 70 minutes after sunset, brilliant Venus, approaching its greatest elongation, is in the west between Regulus and Spica, 29° to Spica’s lower right.  Watch Venus close the gap with Spica during the month.  It is on a shorter and faster solar orbit.  Venus is slowly catching Earth in the same way Earth caught and passed Mars. (From Mars, Earth just passed what we call inferior conjunction for Earth’s inner planets.)  Jupiter is in the south-southwest in Libra, near Zubenelgenubi. Saturn, above the Teapot of Sagittarius, is in the south-southeast as the sky darkens. For the summer season the change of the length of daylight is noticeable during the month.  At the beginning of August, the sun is in the sky for 14 hours, 25 minutes.  With twilight, the dawn to dusk time is 18 hours, 13 minutes.  By month’s end daylight is reduced to 13 hours, 10 minutes and 16 hours, 38 minutes with the three phases of twilight.  Here are the highlights for the beginning of the month:

August 6: The waning crescent moon appears near the Hyades star cluster in the eastern sky before the beginning of morning twilight. Use binoculars to explore the star clusters near the moon.

August 14: The waxing crescent moon appears above Venus and near the star Gamma Virginis in the early evening sky. Venus and Spica are 16° apart.



At mid-month at evening Nautical Twilight (75 minutes after sunset), the four bright planets span the sky from east to west, ranging from Mars in the southeast, Saturn in the south, Jupiter in the southwest, and Venus low in the west.  Venus is near its greatest elongation.  Watch Venus close the gap with Spica for a widely-spaced conjunction at month’s end.  In the morning dim Mercury, only 11° west of the sun, is moving toward a favorable morning greatest elongation at month’s end.  Now, though, it is quite dim, but watch it brighten about 30 times during the next two weeks.  Continue to look for Perseid meteors.  Here’s what’s up during the second half of the month:

August 16: Jupiter passes Zubenelgenubi for the third conjunction during this appearance of the giant planet. The waxing crescent moon is nearby.

August 20: In the early evening sky, Venus and Spica are 10° apart. Venus is 32° to the lower right of Jupiter.

August 27: Mars’ retrograde ends near the asterism Dog’s Country, a kite-shape group in Sagittarius. Look with binoculars when the sky gets dark.

August 31: A Venus-Spica Conjunction. Venus appears 1.2° below Spica.


As the month ends, the summer planet parade begins to lose its brightest planet.  Now setting 85 minutes after sunset, Venus is heading toward its phase of greatest brightness.  Through a telescope, Venus displays a thick evening crescent phase that is 29.5” across.  With Venus near Spica, the pair begins to descend into evening twilight.  Speedy Mercury, now fading from the morning sky, is moving toward its superior conjunction late in September.  Jupiter, visible in the southwest in Libra east of Zubenelgenubi, appears to be heading toward an evening conjunction with Venus.  Watch what occurs next month.  Saturn, slowest moving among the other brighter planets in the planet parade, begins the evening in the south.  Spectacular Mars, shining in the sky nearly all night, starts the evening in the south-southeast.  The moon rises in the east around 10:30 p.m.  When did you first see Sirius in the pre-sunrise sky?  How many Perseids did you see? Did you check your star charts to determine the Perseids’ radiant location? Did you observe the Milky Way?

Exit mobile version