Some daily events in the changing sky for August 10 – 18.

The Perseid meteors appear to diverge from the shower's "radiant" point near the border of Perseus and Cassiopeia — though not all at once as represented here. Under good sky conditions, you might see a meteor about once a minute on average late on the night of the 12th. The best direction to watch is wherever your sky is darkest, not necessarily northeast.

S&T Illustration

Friday, August 10

  • The Perseid meteor shower is just two nights from its predicted peak of activity. Don't miss any chance to look for late-night meteors this weekend if the sky is clear. There's no moonlight to interfere. See our article.

  • If you're out late for the Perseids tonight, you might also catch Algol in eclipse. This bright eclipsing variable star in Perseus should be magnitude 3.4 instead of its usual 2.1 for a couple hours centered on 2:34 a.m. EDT; 11:34 p.m. PDT. Algol takes several additional hours to fade and then to rebrighten. (For a chart and all times of Algol's minima this month, good worldwide, see the August Sky & Telescope, page 53, or our article online.)

    Saturday, August 11

  • 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 10:40 p.m. Eastern Daylight Time. The "red" spot is pale orange. 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. A light blue or green filter helps. (For the times of all Red Spot transits this month, visible worldwide, see the August Sky & Telescope, page 44.)

  • Also on Jupiter: look for Io's tiny black shadow crossing the planet's face from 10:30 p.m. to 12:41 a.m. EDT tonight. Central and western North America have the best views.

    Sunday, August 12

  • New Moon (exact at 7:03 p.m. EDT).

  • The Perseid meteor shower should be at its maximum late tonight. Under dark-sky conditions, you may see a meteor a minute on average. Article.

  • Jupiter's moon Io reappears out of eclipse from Jupiter's shadow around 9:50 p.m. EDT. A small telescope will show it swelling into view just off the planet's eastern (i.e. shadowy) limb.

    Monday, August 13

  • Neptune is at opposition (opposite the Sun in our sky).

  • Algol is at minimum light for a couple hours centered on 11:22 p.m. EDT.

    Tuesday, August 14

  • The red long-period variable stars V and R Ophiuchi, U Cygni, and R Ursae Majoris should be at maximum light (7th or 8th magnitude) this week.

    Wednesday, August 15

  • If you live anywhere in the world's mid-northern latitudes, brilliant Vega crosses the zenith around 10 p.m. daylight saving time (depending on where you are in your time zone). Whenever Vega is at its highest, so is Milky-Way-rich Sagittarius, much lower in the south. And this is also when the Big Dipper and Cassiopeia are balanced at the same height in the northwest and northeast, respectively.

    Thursday, August 16

  • Jupiter's Red Spot should transit around 9:50 p.m. EDT.

    Friday, August 17

  • Look a little above the crescent Moon in late twilight for Spica. Much, much higher above them, and perhaps a bit to the right, shines brighter Arcturus.

    Saturday, August 18

  • Venus is in inferior conjunction, passing 8° south of the Sun.

  • Jupiter's Red Spot should transit around 11:30 p.m. EDT.

    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 standard is Sky Atlas 2000.0) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion or the enchanting though somewhat dated Burnham's Celestial Handbook). Read here how to use them effectively.

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

    This Week's Planet Roundup

    Mercury and Venus are hidden in the glare of the Sun.

    Mars (magnitude +0.4, in Taurus) rises around midnight or 1 a.m. daylight saving time and is and high in the east before dawn. This week it's passing about midway between the Pleiades cluster above it and Mars-colored Aldebaran (a little fainter) below it.

    In a telescope Mars is still only 7.5 arcseconds in diameter, but it's on its way to a Christmas-season opposition, when it will grow to nearly 16 arcseconds wide in the evening sky. However, the dust storm that has encircled the planet for the last month may leave enough haze in the Martian air to reduce our view of Mars's surface even then.

    Incidentally: if friends or family tell you they've read that Mars will become as big and bright as the full Moon later this month, point them to our article about the regular-as-clockwork August Mars Hoax.

    Jupiter on Aug. 2, 2007

    Jupiter is shrinking a bit as Earth pulls away from it, making its features a little harder to resolve. S&T's Sean Walker took this image on Thursday evening, August 2nd (at 1:08 Aug. 3 UT). "Seeing was better than average, but transparency was low," he says. Notice how, as Jupiter moves far from opposition, its celestial east limb is slightly shaded while sunlight strikes the western limb a little more directly.

    S&T: Sean Walker

    Jupiter (magnitude –2.3, in southern Ophiuchus) glares in the south-southwest during twilight and lower in the southwest later after dark. Antares, less bright, sparkles redly 5° below it; the two are evening companions all summer. Other stars of Scorpius shine below them and to the right.

    Saturn is hidden in the glare of the Sun.

    Uranus (magnitude 5.7, in Aquarius) and Neptune (magnitude 7.8, in Capricornus) are well up in the south after midnight.

    Pluto (magnitude 13.9, in the northwestern corner of Sagittarius) is highest right after dark, 18° east-northeast of Jupiter. Finder charts for Uranus, Neptune, and Pluto are in the July Sky & Telescope, page 60.

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

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