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This Week's Sky at a Glance

Some night sky sights for August 24 – September 1

by Alan M. MacRobert

Friday, August 24

  • First-quarter Moon this evening. Look for Antares to its lower left. The other stars of upper Scorpius are scattered around them.

    Right after dark the Sagittarius Teapot stands highest in the south, with the Large Sagittarius Star Cloud above its spout like a puff of steam. Binoculars will show the two nebulae labeled here, before the moonlight gets too bright later this week. Click image for larger view.
    Akira Fujii
  • This evening — before the Moon becomes too bright for the rest of the week — you can still use binoculars to try for the Lagoon and Swan nebulae, M8 and M7, above the Sagittarius Teapot as shown here. To the naked eye, the Teapot is roughly the size of your fist at arm's length.

    Saturday, August 25

  • The Moon at nightfall shines about equidistant from Antares to its lower right and the Teapot of Sagittarius pouring to its left.

    Sunday, August 26

  • The Moon shines above the Sagittarius Teapot in the south after dark.

    Monday, August 27

  • This is the time of year when the Big Dipper, swinging down in the northwest in evening, catches water dumping from the bowl of the dim Little Dipper high above it. Much of the Little Dipper is made of 4th- and 5th-magnitude stars and requires a fairly dark sky.

    Tuesday, August 28

  • As twilight fades, spot Arcturus high in the west. Look far to its lower left for Saturn, Spica below it, and Mars to Saturn's left. This triangle is lengthening each evening Saturn and Spica move to the lower right.

    Wednesday, August 29

  • Fomalhaut, the "Autumn Star," rises in the southeast in mid- to late evening; the time depends on your location. Watch for Fomalhaut coming into view below or lower left of the Moon.

    Thursday, August 30

  • Nearly-full Moon tonight (exactly full at 9:58 a.m. EDT Friday morning). The Moon tonight is in dim Aquarius.

    View in bright dawn
    Mercury and Regulus may not be easy to spot even with binoculars as the sky brightens about 20 minutes before sunrise.
    Sky & Telescope diagram
  • As sunrise approaches on Friday morning, bring binoculars or a wide-field telescope to a spot with a view of the east-northeast horizon to try for the difficult conjunction of Mercury with Regulus, illustrated here.

    Friday, August 31

  • Full Moon (exact at 9:58 a.m. EDT). This is a "blue Moon," when the term means the second full Moon in a calendar month. Blue Moons come every 2.7 years on average. The next is in July 2015.

  • This week, right after dark is the time when the Big Dipper descends to the same height in the northwest as Cassiopeia rises in the northeast. After this, it'll officially be Cassiopeia season.

    Saturday, September 1

  • Look for bright Vega passing the zenith as twilight fades away, if you live in the world's mid-northern latitudes. Vega goes right through your zenith if you're at latitude 39° north (near the latitudes of Baltimore, Kansas City, Lake Tahoe, Sendai, Beijing, Athens, Lisbon).




    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 guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

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

    You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? I don't think so — not for beginners, anyway, and especially not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability). As Terence Dickinson and Alan Dyer say in their invaluable 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 (about magnitude –1.2) remains in view at dawn but lower each day. It's above the east-northeast horizon, far lower left of brilliant Venus. Look about 45 minutes before sunrise, the earlier in the week the better.

    (You can always find your local sunrise/sunset times once you put your location into our online almanac. If you're on daylight saving time, make sure the Daylight Saving Time box is checked.)

    Venus (magnitude –4.3, in Gemini) rises in deep darkness around 3 a.m. daylight saving time (depending on where you are), emerging above the east-northeast horizon like a UFO a good two hours before the first glimmer of dawn. By dawn it's blazing high in the east — vastly outshining Pollux and Castor to its left and Procyon below it or to its lower right.

    Mars, Saturn, and Spica (in Virgo, similar at magnitudes 1.2, 0.8, and 1.0 respectively) form a lengthening triangle low in the west-southwest at dusk. Mars is pulling away to the left of the other two. Look for them far lower left of Arcturus.

    Jupiter on Aug. 23, 2012
    The side of Jupiter away from the Great Red Spot on August 23rd. South is up. The huge, reddish northern-hemisphere belt is resolving itself back into the North Equatorial Belt and, below it here, the North Temperate Belt, with the light North Tropical Zone re-forming between them. Notice the thin, unusual Equatorial Band in the middle of the bright Equatorial Zone.
    Christopher Go
    Jupiter (magnitude –2.3, in Taurus) rises in the east-northeast around midnight daylight saving time. Once it's well clear of the horizon, look for fainter orange Aldebaran twinkling 6° to its right or lower right. By dawn Jupiter shines very high in the southeast, about 35° upper right of even brighter Venus.

    Uranus (magnitude 5.7, at the Pisces-Cetus border) and Neptune (magnitude 7.8, in Aquarius) reach good heights in the southeast by late evening. Finder charts for Uranus and Neptune.

    All descriptions that relate to your horizon — 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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