Sky at a Glance | July 6th, 2012

Dawn view
Worth waking up for: Any time this week, set the alarm to catch the dawn planet drama about an hour before your local sunrise time. (If you're on daylight saving time, make sure the Daylight Saving Time box is checked.)

Friday, July 6

  • The brightest planet action happens at dawn all week, with Jupiter and Venus dramatically stacked in the east-northeast as shown at right. Aldebaran, much fainter, creeps higher close to Venus. Also in the starry background are the Hyades, and above Jupiter are the Pleiades. The asteroids Ceres and Vesta (magnitudes 9.1 and 8.4) are nearby too!

    See article Predawn Treats for Early Risers for the naked-eye aspect, and to find the asteroids in this scene, Ceres and Vesta: July 2012 – April 2013.

    Saturday, July 7

  • The red long-period variable star R Draconis should be at its maximum brightness of about magnitude 7.6 this week. Binoculars should show it. See the article and finder charts in the July Sky & Telescope, page 50.

  • Aldebaran passes 1° to the right or lower right of Venus low in the dawn Sunday through Tuesday mornings.

    Sunday, July 8

  • After nightfall at this time of year, W-shaped Cassiopeia has just passed its lowest point in the north and is beginning its long, slow climb in the north-northeast. The later in the night you look, the more altitude it gains. But the farther south you live, the lower it will be.

    Monday, July 9

  • At nightfall, spot bright Arcturus very high in the southwest to west. It's way above Saturn, Spica, and Mars. Look off to the right of Arcturus for the Big Dipper — which is hanging down and, as night grows late, previewing its late-summer dip as if scooping water.

    Tuesday, July 10

  • As the stars begin to come out, look very high in the east for bright Vega. How soon can you spot the other two stars of the Summer Triangle? Deneb is 24° to Vega's lower left: two or three fist-widths at arm's length. Altair is 34° to Vega's lower right: three or four fists.

    Vega passes the zenith around midnight.

    Wednesday, July 11

  • Altair is the brightest star halfway up the southeastern sky (halfway from the horizon to the zenith). Look to its left by slightly more than a fist-width, and perhaps a bit lower, for the distinctive little constellation Delphinus, the leaping Dolphin. Its nose points left.

    Thursday, July 12

  • By 11 p.m. daylight time the Great Square of Pegasus, signature constellation of autumn, is already up in the east and balancing on one corner.

    Dawn view
    The waning Moon now adds itself to the multifarious dawn scene. (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.)
    Alan MacRobert

    Friday, July 13

  • During dawn on Saturday morning, the waning crescent Moon in the east is upper right of Jupiter and lower right of the Pleiades, as shown here.

    Saturday, July 14

  • During dawn Sunday morning, the waning crescent Moon poses dramatically with Jupiter and Venus, as shown here for North America. Think photo opportunity! The Moon actually occults Jupiter for most of Europe and parts of Asia; map and timetable.


    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).

    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 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.


    This Week's Planet Roundup

    The Sun is displaying a spot group big enough to see without optical aid, just a safe solar filter. I can make out its elongated shape through a #14 arc-welder's shade. Active Region AR 1520 is nearing the midline of the Sun as of Wednesday, meaning it's aimed to blast some serious space weather our way if a big flare happens to erupt within it.

    See a high-res near-real-time image from SOHO, updated every few hours. Also see our article Sunspot 1520 Rolls Into View.

    The dawn sky on July 4th, as captured by Gregg Alliss near Marion, Iowa. He took this 7-second exposure through an 18-mm f/7.1 lens at ISO 800. Click on the image for a larger view.
    Gregg Alliss

    Mercury is disappearing deep in the sunset.

    Venus and Jupiter (magnitudes –4.7 and –2.1) shine dramatically in the east-northeast before and during dawn. They remain stacked 5° or 6° apart this week, with Jupiter on top. Watch Aldebaran, much fainter, moving this week from below Venus to its right. Also in Venus's starry background are the Hyades, and above Jupiter are the Pleiades. The asteroids Ceres and Vesta, magnitudes 9.1 and 8.4, are there too! See article Predawn Treats for Early Risers for the naked-eye aspect, and to find the asteroids, Ceres and Vesta: July 2012 – April 2013.

    Mars (magnitude +0.8, in Virgo) glows orange in the west-southwest at dusk and lower later. It's to the lower right of the Saturn-and-Spica pair by about 20°. It's heading their way; Mars will pass right between Saturn and Spica in mid-August.

    In a telescope Mars is gibbous and very tiny (6.3 arcseconds wide), continuing to fade and shrink.

    Saturn (magnitude +0.7, in Virgo) shines in the southwest as the stars come out. Below it by nearly 5° is Spica. After dark they move lower to the west-southwest.

    Uranus (magnitude 5.8, at the Pisces-Cetus border) and Neptune (magnitude 7.8, in Aquarius) are high in the southeast and south before the first light of dawn. 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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