Sky at a Glance | August 20th, 2010

FLASH! Another white-light flare has been videorecorded on Jupiter, by an amateur in Japan at 18:21:56 UT August 20th. And it's been confirmed from at least one other location. See our article.

Remember the similar event recorded on June 3rd? See Jupiter Takes Another Hit! and The Jupiter Meteor that Didn't Go Splash. Now that lots of people are videorecording Jupiter to make stacked-frame images, are visible impacts turning out to be fairly common?

The path of Psyche's star-shadow across Earth on the morning of August 21st.
Steve Preston

Friday, August 20

  • Good asteroid occultation: in the early-morning hours of Saturday, an 8.4-magnitude star near Aldebaran (in the loose star cluster NGC 1647) will be occulted for up to 10 seconds by the large asteroid 16 Psyche, magnitude 11.1, along a wide path from Texas to Virginia. Maps, times, and finder charts.

    The asteroid-occultation community eagerly seeks accurate timings of such events, especially by video, which is more precise than eyeball timings. Read up on timing methods. If you get involved in this addictive pursuit, join the busy discussion at the occultation Yahoo Group.

    Saturday, August 21

  • The bright eclipsing variable star Algol should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:18 p.m. EDT — when it will be visible from the East Coast low in the northeastern sky. Algol takes several additional hours to fade and to rebrighten. Use our comparison-star chart.

    Sunday, August 22

  • Vega passes nearest the zenith soon after dark at this time of year. Whenever you see Vega there, it means Altair is high in the southeast with its little companion Tarazed almost directly above it. And the Sagittarius Teapot is at its best lower in the south.

    Monday, August 23

  • Arcturus is the brightest star in the west as the stars come out (high above the place where Venus sinks and sets in twilight). At about the same height in the northwest, look for the Big Dipper now turning right-side up. Equally high in the northeast, W-shaped Cassiopeia is climbing.

    Tuesday, August 24

  • Full Moon, the smallest of the year (exact at 1:05 p.m. EDT).

    Wednesday, August 25

  • One of the first deep-sky objects of summer that new telescope owners learn to find is the Ring Nebula, M57, because its location is so well marked in Lyra. But have you looked in on Lyra's other Messier object, the globular cluster M56? See the chart with Gary Seronik's Binocular Highlight article in the August Sky & Telescope, page 45.

    Although they look close together, Jupiter is 1,500 times farther from us than the Moon is when they pass on the 26th and 27th.

    Thursday, August 26

  • The "star" below the Moon late this evening is Jupiter, as shown at right.

    Friday, August 27

  • Low in the west-southwest in twilight, Venus forms the bottom of a flat, symmetrical triangle with much fainter Mars and Spica a little higher. Binoculars help.

  • Jupiter shines to the right of the Moon once they rise after dark, as shown here.

    Saturday, August 28

  • The Venus-Spica-Mars triangle low in the west-southwest in twilight is distorting now, as Spica moves closer to Venus.


    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 map in the center of each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

    Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.
    Alan MacRobert

    Once you get a telescope, to put it to good use you must have a detailed, large-scale sky atlas (set of charts). The standards are the
    Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper Uranometria 2000.0 (stars to magnitude 9.75). And read how to use your charts effectively.

    You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

    Can a computerized telescope take their place? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."


    This Week's Planet Roundup

    Mercury is hidden in the glare of the Sun.

    Venus, though bright at magnitude –4.4, is getting low in the west-southwest during twilight. It sets by dark.

    Mars, vastly dimmer at magnitude +1.5, is a little to Venus's upper right. Look also for similar Spica farther to Venus's upper left for most of the week. Saturn has moved far off to Venus's right or lower right. Bring binoculars for all three of these faint objects.

    Jupiter with Red Spot and Red Spot Jr., Aug. 13, 2010
    By August 13th, Jupiter's Oval BA (Red Spot Junior) had nearly caught up with the Great Red Spot and was about to pass it. Also note the ghostly tan and blue-gray signs of the broad South Equatorial Belt hidden under white clouds. These traces now include the outline of the Red Spot Hollow just below the spot. South is up.


    Christopher Go took this stacked-video image at 18:03 UT Aug. 13, 2010.

    Alan MacRobert

    Jupiter (magnitude –2.8, in Pisces) rises in late twilight and is well up in the east-southeast before midnight. It's highest in the south around 2 or 3 a.m. daylight saving time — the brightest starlike point in the morning sky.

    Jupiter's Great Red Spot is near System II longitude 150°. Assuming it stays there, here's a list to print out of all the Great Red Spot's predicted transit times for the rest of 2010.

    FLASH! Another white-light flare has been videorecorded on Jupiter, by an amateur in Japan at 18:21:56 UT August 20th, and it's been confirmed from at least one other location. See our article.

    Remember the similar event recorded on June 3rd? See Jupiter Takes Another Hit! and The Jupiter Meteor that Didn't Go Splash. Now that lots of people are videorecording Jupiter to make stacked-frame images, are visible impacts turning out to be fairly common?

    Uranus (magnitude 5.8, in Pisces) is about 2° west of Jupiter. In a telescope Uranus is only 3.7 arcseconds wide, compared to Jupiter's unusually wide 48″.

    Neptune (magnitude 7.8, at the Aquarius-Capricornus border) is up high by mid- to late evening. See our finder charts for Uranus and Neptune in 2010.

    Pluto (magnitude 14, in northwestern Sagittarius) is highest in the south right after dusk, but the bright Moon interferes this week. (See our Pluto finder charts in the July Sky & Telescope, page 60.)


    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 (also known as UT, UTC, or GMT) minus 4 hours.


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