This Week’s Sky at a Glance

Supernova in M74. The supernova that was discovered in the spiral galaxy M74 last week had reached about magnitude 12.3 by August 2nd. M74 is in Pisces, well up in the eastern sky in the early-morning hours. See article with finder photo: Supernova Erupts in M74.


Friday, August 2

  • As summer begins to wane, The Big Dipper hangs diagonally on the wall of the northwestern sky during evening. It's about as high as bright Arcturus, shining to its left in the west.

    Watch the dawn Moon wane past the row of Jupiter, Mars, and Mercury. The Moon's positions are plotted for the middle of North America. Bring binoculars; the visibility of faint objects in bright twilight is exaggerated here.
  • In early dawn Saturday morning (you can set your alarm), the waning crescent Moon hangs to the upper right of Jupiter, Mars, and Mercury low in the east-northeast, as shown at right.

    Saturday, August 3

  • During Sunday dawn an even thinner waning Moon poses to the right of the Jupiter-Mars-Mercury line, as shown at right.

    Sunday, August 4

  • The asteroid 3 Juno is brightest at opposition this week, glimmering at magnitude 9.0 at the Aquarius-Aquila border. Pick it up with your scope using the finder chart in the August Sky & Telescope, page 51.

    Monday, August 5

  • The little constellation Scutum, off the tail of Aquila, is faint to the naked eye but important for its super-rich Milky Way field and its deep-sky objects. See Fred Schaaf's "The Shield of King Sobieski" in the August Sky & Telescope, page 47.

    Tuesday, August 6

  • A binocular challenge: Spot Venus in twilight low in the west and then, using binoculars, see if you can detect the 4.0-magnitude star that it's closely passing. The star is Sigma Leonis, Leo's hind foot, just 0.6° above Venus depending on your time and location.

  • New Moon (exact at 5:51 p.m. Eastern Daylight Time).

    Wednesday, August 7

  • Bright Vega passes closest to overhead around 10 or 11 p.m., depending on how far east or west you are in your time zone. How closely it misses your zenith depends on how far north or south you live. It passes right through the zenith if you're at latitude 39° north (Washington DC, Cincinnati, Kansas City, Lake Tahoe). How closely can you judge this by looking?

    Thursday, August 8

  • The Perseid meteor shower is ramping up! It should peak late this Sunday and Monday nights. See our article Get Ready for the 2013 Perseids and make your plans.

    Back in the evening sky, the waxing crescent Moon passes Venus and Saturn.

    Friday, Aug. 9

  • Early in twilight, about a half hour after sunset, look very low in the west below Venus for the thin crescent Moon, as shown at right. Binoculars will help.

    Saturday, Aug. 10

  • The waxing crescent Moon shines well to the left of Venus low in twilight, as shown here. Keep watching on subsequent evenings as more and more of the Moon's sunlit side turns our way, what with the Moon increasing its angular separation from the Sun.



    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.

    This is an outdoor nature hobby. 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).

    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.

    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 beloved if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means heavy and expensive). 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, Mars, and Jupiter shine in the east-northeast before and/or during dawn. Jupiter is the highest and brightest (magnitude –1.9). Look for faint Mars (magnitude +1.6) to Jupiter's lower left. Look lower left of Mars as dawn begins to brighten for Mercury (brightening from magnitude 0 to —1 this week, but sinking lower).

    Castor and Pollux are to their left, and Orion is much farther to their right.

    Venus (magnitude –3.9) shines brightly very low in the west in evening twilight. In a telescope Venus is still small (13 arcseconds) and gibbous (81% sunlit).

    Double-shadowed Saturn. Saturn is near eastern quadrature during July and August (90° east of the Sun), so this is when its globe casts the widest shadow onto the rings behind as seen from Earth's viewpoint. That's the black band on the rings just off the globe at lower right of center (celestial northeast).

    Meanwhile, the rings are now casting a prominent shadow onto the globe. That's the black rim above the rings here (south is up). Both shadows add to Saturn's 3-D appearance in a telescope.

    The gray band on the globe just inside the rings is the semitransparent C Ring, the sparse "Crepe Ring," with no shadow currently behind it to confuse its appearance.

    Damian Peach took this excellent image on July 19th using the powerful stacked-video method. Don't expect Saturn to look this clear and crisp in any telescope visually!


    Saturn (magnitude +0.7, in Virgo) glows in the southwest as twilight fades, with Spica 12° to its lower right. As night grows darker look almost as far to Saturn's left for fainter Alpha Librae.

    Uranus (magnitude 5.8, in Pisces) and Neptune (magnitude 7.8, in Aquarius) are nicely placed in the southeast to south after midnight. 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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