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This Week's Sky at a Glance

by Alan M. MacRobert

Some daily events in the changing sky for August 8 – 16.

Watch the bright waxing Moon cross Scorpius and Sagittarius after dark this week. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times actual size.)
Sky & Telescope diagram
Friday, August 8

  • First-quarter Moon (exact at 4:20 p.m. EDT).

  • Already you're likely to see occasional Perseid meteors from late evening on through the night. The Perseid shower should peak on the morning of August 12th, but it actually runs from many days before then to several days after. Tonight the moonlight isn't as much of a problem as it'll become in a few days; the Moon sets around 11 p.m. or midnight daylight saving time.

    Saturday, August 9

  • The Moon is just under the head of Scorpius tonight, as shown above. Look for orange Antares, with its two fainter outlier stars, to the Moon's left at nightfall.

  • Jupiter's Great Red Spot should cross Jupiter's central meridian (the imaginary line down the center of the planet's disk from pole to pole) around 12:19 a.m. Sunday morning Eastern Daylight Time; 9:19 p.m. Saturday evening Pacific Daylight Time. The "red" spot appears very pale orange-tan. It should be visible for at least 50 minutes before and after in a good 4- or 6-inch telescope if the atmospheric seeing is sharp and steady, which it usually isn't. A blue or green filter helps. For all Red Spot transit times, good worldwide, see our listing or applet online.

    Sunday, August 10

  • Antares shines to the right of the waxing gibbous Moon this evening, as shown above.

    Monday, August 11

  • The Perseid meteor shower should be at its peak late tonight. Best time to watch: between moonset (around 1 or 2 a.m.) and the first light of dawn Tuesday morning. See our article.

    (To find your local times of moonset and the start of dawn on any date, make sure you've put your location and time zone into our online almanac. If you're on daylight saving time like most of North America, make sure the Daylight Saving Time box is checked.)

  • While you're watching for Perseids tonight, keep an eye on Algol, Beta Persei! This famous eclipsing binary star should be at minimum light, magnitude 3.4 instead of its usual 2.1, from about 2 to 4 a.m. Tuesday morning EDT. Algol takes several additional hours to fade and to rebrighten. Here's a naked-eye comparison-star chart.

    Tuesday, August 12

  • Bright Venus and faint Saturn are less than 1° apart this evening and tomorrow evening, low in the glow of sunset. Use binoculars.

  • Jupiter shines upper left of the Moon, as shown above. And if you're in the middle of North America at nightfall, the Moon is then in the middle of the Sagittarius Teapot's lid.

  • Jupiter's Red Spot should transit around 9:49 p.m. EDT.

    Wednesday, August 13

  • Jupiter shines upper right of the Moon. Although they look close together, Jupiter is actually almost 2,000 times farther away. And it's 40 times larger in diameter!

    Looking low in the west in bright twilight
    Watch Venus, Mercury, Saturn, and Mars change configuration daily low in bright twilight. Bring binoculars!
    Sky & Telescope diagram
    Thursday, August 14

  • Saturn is equidistant from Venus and Mercury low in the sunset, as shown at right.

  • Mars is passing a few arcminutes from the 3.6-magnitude star Beta Virginis (at the time of twilight for the Americas). They should make a fine pair in a telescope.

  • Jupiter's moon Io disappears behind Jupiter's western limb at 9:48 p.m. EDT, then reappears out of eclipse by the planet's shadow (just off Jupiter's eastern limb) around 12:54 a.m. EDT. By then Jupiter will be getting low for easterners, but it will be beautifully placed for westerners, where the time is 9:54 p.m. Pacific Daylight Time. (For a list of all events among Jupiter's moons this month, visible worldwide, see the August Sky & Telescope, page 58.)

  • Jupiter's Red Spot should transit around 11:27 p.m. EDT.

    Friday, August 15

  • There's an interesting coincidence all month. Every night, bright Jupiter passes its highest due south right about when Vega passes its highest overhead.

  • Neptune is at opposition.

    Saturday, August 16

  • Mercury is equidistant from Venus and Saturn after sunset, as shown at lower right.

  • Full Moon (exact at 5:16 p.m. EDT).

  • A partial lunar eclipse can be seen tonight from most of the inhabited world except North America! See article.

    Keep watching as Mercury closes in on Venus. They'll appear closest together (at appulse) on the 20th, when they'll be 1° apart.
    Sky & Telescope diagram


    Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly foldout map in each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

    Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of maps; the standards are Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.

    More beginners' tips: "How to Start Right in Astronomy".



    This Week's Planet Roundup

    Mercury (fading from magnitude –1 or –0.5 this week) is in deep in the glow of sunset, approaching much-brighter Venus from the lower right. Look with binoculars about 30 minutes after sunset; see the panels above.

    Venus (magnitude –3.8) is still deep in the glow of sunset. Look for it just above the west-northwest horizon 30 minutes after sundown. Fainter Mercury and much-fainter Saturn are passing near it, as shown above.

    Mars (a dim magnitude +1.7) is low after sunset, roughly a fist-width at arm's length to the upper left of Venus and company. Use binoculars.

    Jupiter on August 5th
    A diagonal white rift has appeared in Jupiter's dark North Equatorial Belt (below center), as seen in this stacked-video image taken August 5th by Christopher Go in the Philippines. Similar diagonal rifts, tilted the other way, are near the same longitude in the South Equatorial Belt, above center. The System II longitude at the time of the picture was 43°. The Great Red Spot was just around the limb; it's currently near System II longitude 127°. South is up, to match the south-up view in many telescopes.
    Christopher Go
    Jupiter (magnitude –2.6, in Sagittarius) shines brightly with a steady glare in the south during evening. It's upper left of the Sagittarius Teapot and just below the bowl of the smaller, dimmer Teaspoon. It's due south and highest around 10 p.m. daylight saving time (depending on how far east or west you live in your time zone).

    Saturn (magnitude +0.8) is just upper left of Venus at the beginning of the week, passes Venus closely on August 13th, and then moves to its lower right near Mercury. See the panels above.

    Uranus and Neptune (magnitudes 5.7 and 7.8, respectively, in Aquarius and Capricornus) are well up in the southeast by 11 p.m. Use our article and finder charts. Neptune is at opposition on August 15th.

    Pluto (magnitude 14.0, in the northwestern corner of Sagittarius) is in the south after dark. If you've got a big scope and a dark sky, use our article and finder chart.

    All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (known as UT, UTC, or GMT) minus 4 hours.

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