Sky at a Glance | May 6th, 2011

Friday, May 6

  • The crescent Moon shines in the west after dark. The brightest star far to the Moon's upper right is Capella. Less far to the Moon's lower left, look for Betelgeuse sinking away for the season.

    View in bright dawn, very low
    The dawn planet configuration before Sunday sunrise. (The visibility of the faint objects in bright twilight is exaggerated.) To view this scene for any day in May, watch our animation and pause it on the day of your choice. (The scene is oriented for a skywatcher near 40° north latitude.)
    Sky & Telescope
  • From tomorrow morning through the 15th, binoculars show Mercury less than 1½° lower right of Venus, with Jupiter fitting into the same 5° field of view. Track their changes each clear morning!

    Saturday, May 7

  • The Moon shines in Gemini this evening below Pollux and Castor. Left of the Moon is Procyon. Right of the Moon is bright Capella, with Menkalinen to its upper left. These five stars form an enormous arch over the lunar crescent at dusk. This is an archetypal springtime scene, repeated every April and May when the Moon is a waxing crescent.

  • A small telescope will show Titan, Saturn's largest moon, about four ring-lengths to Saturn's west tonight. A 6-inch telescope begins to show the orange color of its smoggy atmosphere.

    Sunday, May 8

  • The Moon this evening forms a big, curving arc with Procyon to its lower left and Pollux and Castor to its upper right.

  • The 9th-magnitude asteroid 10 Hygiea, currently near opposition, is passing through southern Libra this month. Hygiea is the fourth-largest asteroid; it appears as dim as it does because its surface is quite black. See the finder chart and article in the May Sky & Telescope, page 56.

    Monday, May 9

  • On spring evenings the Big Dipper turns over as if to dump spring rains on the world, or so it appears to Northern Hemisphere skywatchers. Look for the Dipper very high in the northeast as the stars come out.

    Tuesday, May 10

  • First-quarter Moon (exact at 4:33 p.m. Eastern Daylight Time). Look above the Moon this evening for Regulus and the Sickle of Leo.

  • Before sunrise Wednesday morning, Jupiter and Mercury are, respectively, just ½° above and 1½° below brighter Venus. This is also when Jupiter and Venus — the two brightest planets — will appear closest together.

    Wednesday, May 11

  • Regulus and the Sickle of Leo are to the Moon's upper right after dark.

    The waxing gibbous Moon passing under Saturn and Spica.

    Thursday, May 12

  • The three brightest stars in the spring evening sky are Arcturus, now high in the southeast, Vega lower in the northeast, and Capella in the northwest. All are zero magnitude. Vega and Capella are at exactly the same height sometime around 10 p.m. daylight saving time tonight, depending on your location. How accurately can you time this event for where you live?

    Friday, May 13

  • The Moon is far to the lower right of Saturn this evening, as shown here.

    Saturday, May 14

  • Now the Moon is now lower right of Spica, as shown here.


    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 sky 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, Venus, Mars, and Jupiter are deep in the bright glow of dawn. Use binoculars 20 or 30 minutes before sunrise; look low in the east. Venus is by far the brightest. Second-brightest is Jupiter, which passes 0.6° from Venus on the morning of May 11th (for the time zones of the Americas). Below Venus all week is brightening Mercury. Faint little Mars is a challenge object to their lower left.

    See our article about the whole month of this continuing dawn parade, with daily panels in an animation. You can pause the animation at your date of choice.

    Saturn on April 26, 2011
    Saturn's white spot has erupted again! The head of the pale streamer wrapping around the planet has brightened up, as seen in this image taken by Christopher Go on April 26th (at 12:54 UT; System III central-meridian longitude 274°). Compare with Go's images of the area one day earlier (scroll down to "April 25").


    Also see his animation there of several images confirming dark spokes on the left (celestial west) side of the bright B ring on April 25th. On his website, images are north up.


    Saturn (magnitude +0.6, in Virgo) is the only planet in good telescopic view. Look for it high in the southeast as the stars come out, with Spica twinkling to its lower left and bright Arcturus about twice as far to its upper left. Saturn shines highest in the south around 10 or 11 p.m. daylight saving time — not long after dark now.

    In a telescope, Saturn's rings have narrowed slightly in the last few months to 7.6° from edge on. The pointlike source of Saturn's months-old white streak has rebrightened, as imaged here. See how many of Saturn's satellites you can identify in your scope using our Saturn's Moons tracker.

    The fainter star Gamma Virginis (Porrima) is only about 1° upper right of Saturn after dark. Gamma Vir is an attraction in its own right: a fine, close telescopic binary star with a current separation of 1.7 arcseconds. Use high power and hope for good seeing. See article in the April Sky & Telescope, page 56. Saturn will keep closing in on Gamma Vir until passing 0.4° from it in mid-June.

    Uranus (magnitude 5.9, in western Pisces) is still in the dawn glow.

    Neptune (magnitude 7.9, in Aquarius) is low in the southeast just before dawn's first light.


    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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