During the first week of August, Mercury will be visible very low in the eastern pre-dawn sky as a magnitude -0.9 object. Viewed in a telescope during that time, the planet will exhibit a waxing gibbous phase and a diminishing apparent disk size. It will be descending sunward, and will disappear into the sun's glow well before it reaches superior conjunction on Aug. 17. Mercury will re-appear low in the western sky after sunset for the final week of the month. This time, the planet will show a waning, nearly fully-illuminated phase, and a disk size of approximately 5 arc-seconds.
During August, Venus will shine very brightly in the eastern pre-dawn sky. For the first half of the month, it will move prograde east through the stars of eastern Taurus and then through northern Orion. On Aug. 13, Venus will reach its greatest separation, 46 degrees west of the sun, as it crosses into Gemini, where it will remain until early September. The planet will diminish slightly in visual brightness during August. Viewed in a telescope, Venus will exhibit a half-illuminated phase, and its apparent disk diameter will shrink from 27 to 20 arc-seconds. On Aug. 15, a pretty, waning crescent moon will take up a position 3.5 degrees to the celestial north of Venus, setting up a nice photo opportunity.
During August, Mars will shine prominently among the modest stars of Pisces in the late evening and overnight sky as the Earth continues to overtake the reddish planet. Visually, Mars will nearly double in brightness during August — from magnitude -1.1 on Aug. 1 to magnitude –1.8 on the 31st. Meanwhile, its apparent disk size will grow from 14.5 to 19 arc-seconds. On Saturday night, Aug. 8, the waning last quarter moon will pass only two finger widths to the lower right (or 2.3 degrees to the celestial southwest of) Mars. They will not set in the west until mid-morning on Sunday — offering a chance to see Mars in the morning daytime sky using binoculars and backyard telescopes, by using the moon as a reference.
During August, Jupiter will already be shining low in the southeast when the evening sky begins to darken. Recently past opposition, the planet will be a fine observing target all night long as it moves retrograde westward through the stars of northeastern Sagittarius — and only 8 degrees to the west of dimmer Saturn. During August, Jupiter will decrease slightly in brightness (from magnitude -2.71 to -2.55) and in apparent disk size (from 47 to 44 arc-seconds). On Aug. 1 the nearly full moon will sit to the celestial south of Jupiter and Saturn — a grouping that will make a beautiful wide field image. The tableau will repeat on Aug. 28. Commencing at 10:30 p.m. EDT on Friday evening, Aug. 14 (or 02:30 GMT on Saturday, Aug. 15), observers in the Central Time zone, and east of there, can watch Ganymede's round, black shadow and the Great Red Spot travel across Jupiter's northern and southern hemispheres, respectively. Commencing at 12:06 a.m. EDT (or 04:06 GMT) on Saturday, Aug. 15, observers in the Americas can witness a rare double shadow transit when Io's and Ganymede's shadows cross Jupiter accompanied by the Great Red Spot! On Saturday, Aug. 22, observers in the western half of North America can watch the shadows of Io and Ganymede transit Jupiter together starting at 1:32 a.m. EDT (or 06:32 GMT).
After its recent opposition, Saturn will be well-positioned for observing all night during August while it moves retrograde (westward) through the stars of northeastern Sagittarius. The planet will also remain just 8 degrees to the east of Jupiter, which will outshine Saturn by a factor of 10 — delaying the dimmer planet's appearance, low the southeastern sky, until well after sunset. The rings, and many of Saturn's moons, are easily visible in backyard telescopes. During August, Saturn will diminish slightly in brightness and apparent size. On Aug. 1 the nearly full moon will sit just to the celestial south of Jupiter and Saturn — a grouping that will make a beautiful wide field image. The tableau will repeat on Aug. 28 — and then the gibbous moon will shift to sit 6 degrees southeast of Saturn the following night.
As August begins, blue-green Uranus (magnitude 5.8) is transitioning from a post-midnight object to an evening object — eventually rising at 10 p.m. local time by month-end. On Aug. 15, Earth's faster orbit will cause Uranus to cease its eastward motion with respect to the distant stars of southern Aries, and begin a westward retrograde loop that will last until January, 2021. The slow-moving planet can be found by looking 10 degrees south of Aries' brightest star Hamal. On the night of Aug. 10-11, the last quarter moon will be positioned 5 degrees below (southeast) of Uranus.
During August, Blue-tinted Neptune (magnitude 7.8) will be visible from late evening onward in the southeastern and southern sky — moving retrograde (westward) among the stars of eastern Aquarius. The planet will be moving toward that constellation's naked-eye star Phi (φ) Aquarii, some three degrees to Neptune's west.
Editor's note: If you have an amazing skywatching photo you'd like to share for a possible story or image gallery, please contact managing editor Tariq Malik at firstname.lastname@example.org.
Monthly skywatching information is provided to Space.com by Chris Vaughan of Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu and Chris at @Astrogeoguy.