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Eclipse, at last: the "Great American" total solar eclipse is this month's star attraction.

Are you ready to be awed? On Monday August 21st, the Moon paints a streak of deep midday darkness from Oregon to South Carolina with a swift and narrow brush of umbra during the long-awaited "Great American" total eclipse of the Sun. All of the Americas north of the equator get a partial eclipse. This month also features a partial lunar eclipse for the opposite side of the world, visible across most of the Eastern Hemisphere on the night of August 7-8.

But what are the planets up to in this month of Sun and shadow? Jupiter appears in the west-southwest at nightfall and sets in late evening. Saturn shines in the south at dusk and sets in the middle of the night. Venus rises an hour or so before morning twilight begins, beaming high in the east as sunrise nears. Mars and Mercury are too near the Sun for viewing this month, outside of the brief minutes at totality during the solar eclipse.


Mars was in conjunction with the Sun on July 27th and is lost from view in the solar glare throughout August--except when its 1.8-magnitude light might be glimpsed about 8[degrees] right of the Sun during the total eclipse on August 21st. Brilliant Venus, a bit more than four times farther right from the Sun than Mars, will be easy to see during totality. Depending on the transparency of your sky, you may be able to catch Venus when the Sun is only 85-90% covered by the Moon. Mercury, at 4th magnitude, shines too faintly, and Jupiter, about 77[degrees] from the Sun, is bright but low in the southeast. Most tantalizing is Regulus, magnitude 1.4, only about 1[degrees]left of the eclipsed Sun's disk. That's about two solar diameters. Binoculars will help.


Jupiter declines from about 22[degrees] to 11[degrees] high in the southwest when observed 45 minutes after sunset in August. Jupiter fades from magnitude -1.9 to -1.7 and its disk shrinks from about 34" to 32" wide over the course of the month. The gap between Jupiter and Spica narrows from about 8[degrees] to 4[degrees]. On August 10th binoculars show Jupiter at its closest (0.6[degrees]) to 4th-magnitude Theta ([theta]) Virginis.

Saturn, magnitude +0.4, hovers in southeastern Ophiuchus this month, glowing at its highest (about 27[degrees]) due south in late twilight.

Saturn's rings will appear slightly more open in October, when they reach maximum tilt (27.0[degrees]) from our perspective for the first time since 2002. But we can catch Saturn higher at nightfall now, when the ring tilt is essentially the same. The planet's globe shrinks only slightly in the eyepiece this month, from 18" to 17" in equatorial diameter.

Saturn becomes stationary in right ascension and ecliptic longitude on August 25th. The next day, the magnitude +0.4 world stands a minimum 12.6[degrees] upper left of distinctly less bright Antares; it then starts moving away from the star with direct (eastward) motion.


Neptune, in Aquarius, rises during evening twilight and finishes the month just days from opposition. The 8th-magnitude ice giant transits about 3 a.m. daylight-saving time at the beginning of the month, 1 a.m. by the end.

Uranus, two magnitudes brighter than Neptune, awaits you in Pisces. It rises in the late evening and is highest just before morning twilight. Check for finder charts for both Neptune and Uranus.


Venus comes up roughly 3 hours before the Sun in August, long before the very first sign of dawn, shining at magnitude -4.0 in the first half of the month and -3.9 in the latter half. Its gibbous phase thickens to 83% lit, while its apparent diameter shrinks from 14 1/2" to 12 1/2".

Venus was at greatest elongation west of the Sun back on June 3rd but reaches its greatest sunrise altitude, about 30[degrees] high, on August 2nd for skywatchers near latitude 40[degrees] north. That morning, binoculars or telescope show the big open cluster M35 just 2 1/2[degrees] upper left of Venus.

The resplendent planet spends most of the month crossing Gemini. On the morning of August 17th, Venus blazes 1[degrees] directly below Delta ([delta]) Geminorum and 8[degrees] right of Pollux. By the morning of August 25th, Venus has crossed into Cancer, where the planet ends the month as it began: on the verge of passing a big open star cluster, in this case M44, the Beehive.


The waxing gibbous Moon shines about 3[degrees] or 4[degrees] upper right of Saturn on the evening of August 2nd. The Moon is partially eclipsed for most of the Eastern Hemisphere on the night of August 7-8; see page 50.

The waning crescent Moon is close to Aldebaran as they rise on the night of August 15-16. A much thinner lunar crescent hangs directly below Venus on the morning of August 19th. A still thinner crescent may be viewable with binoculars the next morning, far lower left of Venus.

The Sun is totally eclipsed by the new Moon on August 21st; see pages 20 and 48 for more.

The waxing crescent Moon hop-scotches past Jupiter and Spica on the evenings of August 24th and 25th. It passes Saturn on the evenings of August 29th and 30th.

* To find out what's visible in the sky from your location, go to

* Contributing Editor FRED SCHAAF welcomes your letters and comments at

Caption: These scenes are drawn for near the middle of North America (latitude 40[degrees] north, longitude 90[degrees] west); European observers should move each Moon symbol a quarter of the way toward the one for the previous date. In the Far East, move the Moon halfway. The blue 10[degrees] scale bar is about the width of your fist at arm's length. For clarity, the Moon is shown three times its actual apparent size.

Caption: ORBITS OF THE PLANETS The curved arrows show each planet's movement during August. The outer planets don't change position enough in a month to notice at this scale.

Caption: Dawn, Aug 15-17 Looking East-Southeast, halfway up

Caption: Aug 21 Looking South-Southwest, high in the sky

Caption: Dusk, Aug 24-26 Looking West-Southwest
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Title Annotation:Sun, Moon & Planets
Author:Schaaf, Fred
Publication:Sky & Telescope
Date:Aug 1, 2017
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