Venus, Pollux, and Castor line up straight as trilight fades on Friday June 11th.

Sky & Telescope diagram


Dawn Comet. The comet C/2009 R1 (McNaught) is now having its period of best visibility, as it crosses Perseus low in the northeast just before the start of dawn. It's 5th magnitude and brightening. Binoculars are showing it nicely, but a telescope does better. See our article and finder chart.

Friday, June 11

  • As dusk falls this evening, bright Venus forms a straight line with Pollux and Castor to its right, as shown here. The line is just over 10° long.

    Saturday, June 12

  • New Moon (exact at 7:15 a.m. Eastern Daylight Time).

    Sunday, June 13

  • The asteroid 1 Ceres comes to opposition this week, shining at magnitude 7.2. It's in Sagittarius, having passed by the Lagoon Nebula two weeks ago. In late evening, once Sagittarius gets high, spot Ceres (and the Lagoon!) with binoculars using our article and finder chart: Ceres in 2010. In February 2015, NASA’s Dawn spacecraft will rendezvous with Ceres and take up orbit around it, revealing a whole new world (a "dwarf planet" by current nomenclature) in detail.
  • Titan, the largest and brightest moon of Saturn, is at its eastern elongation from Saturn this evening and tomorrow evening. A small telescope will show it.

    Mars, Regulus, Moon

    Mars and Regulus are drawing apart by the time the Moon meets them.

    Sky & Telescope diagram


    Monday, June 14

  • The thin crescent Moon hangs 4° or 5° below Venus in the west-northwest at dusk, as shown here.
  • Comet McNaught is near Delta Persei and the Alpha Persei Association just before dawn Tuesday morning.

    Tuesday, June 15

  • With the official start of summer just six days away, bright Scorpius is already sticking up in the south-southeast after dark.

    Wednesday, June 16

  • Mars and Regulus form a flattened, tilted triangle with the waxing Moon, as shown here.

    Thursday, June 17

  • Mars and Regulus are to the right of the Moon this evening. Saturn glows to the Moon's upper left.

    Friday, June 18

  • The "star" about 9° above the Moon this evening is the planet Saturn, as shown below.

    Saturday, June 19

  • Dazzling Venus is less than 1° from the dim Beehive Star Cluster, M44, this evening and tomorrow evening. Look with binoculars or a good finderscope right at the end of dusk.
  • Saturn is at quadrature, 90° west of the Sun.

    Moon, Saturn, and Spica

    Waxing past first quarter, the Moon marches eastward below Saturn and Spica.

    Sky & Telescope diagram

    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.

    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


    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 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 (about magnitude –0.7) is having a poor apparition very low in the east-northeast at dawn. As the sky grows bright, scan for it with binoculars very far lower left of Jupiter. Don't confuse it with twinkly Capella, which is far to Mercury's left and perhaps (depending on your latitude) higher.

    Venus (magnitude –4.0, moving from Gemini into Cancer) is the bright Evening Star shining in the west-northwest during and just after twilight. Look for Pollux and Castor to its right or lower right.

    In a telescope, Venus is still a small (14-arcsecond) gibbous disk. It's so dazzling, in its brilliant illumination by the Sun, that you'll have the cleanest telescopic views of it in the bright blue sky before sunset — if you can find it then. Not until late summer does Venus assume its larger and more dramatic crescent phase.

    Mars (magnitude +1.2, in Leo) still forms a striking pair with bluer Regulus (magnitude +1.4) at the beginning of the week, but every day it's moving farther to Regulus's east. The star to their upper right is Gamma Leonis, not much dimmer.

    In a telescope Mars is just a very tiny blob, 5.8 arcseconds in diameter.

    Jupiter on May 30, 2010

    Jupiter's Great Red Spot is still floating free in the practically nonexistent South Equatorial Belt. Imager Christopher Go notes that the spot's south rim was especially dark. The slightly orange smudge to the upper right is Oval BA, "Red Spot Junior." South is up.

    Go took this image at 20:37 UT May 30th, when the Great Red Spot had just crossed Jupiter's central meridian. the central meridian longitude (System II) was 157°.

    Christopher Go


    Jupiter (magnitude –2.4, below the Circlet of Pisces) rises around 1 or 2 a.m. daylight saving time and shines high in the southeast before dawn. Nothing else there is nearly so bright. See our articles about Jupiter's disappearing South Equatorial Belt and about the apparent meteor in its atmosphere that was filmed on June 3rd.

    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.

    Saturn (magnitude +1.1, in the head of Virgo) glows in the southwest during evening. The diagonal line of Saturn, Mars, and Venus is shrinking week by week. The three planets will bunch up low in the sunset in early August.

    In a telescope Saturn's rings are tilted a mere 1.8° from edge-on. Not until 2024 will the rings again appear this thin. Note the thin black shadow-line that the rings cast on Saturn's globe.

    Uranus (magnitude 5.9) is within about 1° of Jupiter. In a telescope Uranus is only 3.5 arcseconds wide, compared to Jupiter's 40″.

    Neptune (magnitude 7.9, at the Aquarius-Capricornus border) is in view during early morning hours well to Jupiter's west. See our finder charts for Uranus and Neptune in 2010.

    Pluto (magnitude 14, in northwestern Sagittarius) is highest in the south after midnight. See our Pluto finder charts for 2010.

    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.

    To be sure to get the current Sky at a Glance, bookmark this URL:
    http://SkyandTelescope.com/observing/ataglance?1=1

    If pictures fail to load, refresh the page. If they still fail to load, change the 1 at the end of the URL to any other character and try again.

    • About Alan MacRobert

    Alan M. MacRobert became an avid Sky & Telescope subscriber in 1966 at age 14, joined the editorial staff in 1982, and is now a senior contributing editor, semi-retired. He played a role in practically every part of the magazine and the company's other products for more than a generation, both on the amateur-observing side and the science-reporting side. In 1994 a book collection of his observing how-tos and telescopic sky tours was published as Star Hopping for Backyard Astronomers. He has produced This Week's Sky at a Glance online every week since 1989.

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