Friday, April 8

  • Arcturus, the "Spring Star," is the brightest point shining high in the east these evenings. If you wait up until about 10 or 10:30 you can log an early sighting of Vega, the equally bright "Summer Star," rising low in the northeast.

    Saturday, April 9

  • The Moon, in the feet of Gemini, is a very thick crescent less than two days from first quarter. If your sky is really clear after dark, binoculars will show the star cluster M35 roughly 2° to the Moon's upper right (for North America). In binoculars it's a largish, dim glow. In a telescope it's a city of stars.

    Sunday, April 10

  • Lunar occultation: Skywatchers in eastern North America this evening can watch the dark limb of the first-quarter Moon snap up Zeta Geminorum, magnitude 3.8. Some times: Toronto, 9:10 p.m. EDT; Washington DC, 9:17 p.m. EDT; Atlanta, 9:09 p.m. EDT; Miami, 9:29 p.m. EDT. Map and timetables for many more locations. In some places the occultation happens in twilight and you'll need a telescope.

    Monday, April 11

  • First-quarter Moon (exact at 8:05 a.m. Eastern Daylight Time).

    Tuesday, April 12

  • Early spring is when Orion tilts downward in the southwest after dusk, with his three-star belt turning horizontal as seen from north temperate latitudes. The belt points left toward bright Sirius and to the right more or less toward orange Aldebaran. Right of Aldebaran are the Pleiades.

    Wednesday, April 13

  • Look for Regulus in Leo about 6° above or upper left of the Moon this evening (for North America).
  • A small telescope will always show Titan, Saturn's largest moon. Tonight Titan is four ring-lengths to Saturn's east. Saturn's other major satellites are all close to the planet tonight.

    Thursday, April 14

  • Look very high in the northeast after dark for the Big Dipper standing on its handle and tipping over to the left. The two stars forming the front of its bowl, the Pointers, point lower left to Polaris about three fists at arm's length away.

    Equally far on the other side of Polaris from the Big Dipper is Cassiopeia, now swinging low and turning into a W rather than an M.

    Twilight view southeastward

    As the Moon waxes to full, it teams up with Saturn in the evening sky.

    Sky & Telescope diagram

    Friday, April 15

  • The nearly full Moon is approaching Saturn and company in the southeastern sky, as shown here.
  • So you know the Big Dipper's Pointer stars point to Polaris. Follow the Pointers backward in the opposite direction (by a greater distance), and you'll land in Leo.

    Saturday, April 16

  • Saturn and Gamma Virginis (Porrima) are upper left of the nearly full Moon this evening, as shown here. They're currently 2½° apart; they'll close up in the coming weeks. Gamma Vir is a close, equal double star, currently with a separation of 1.7 arcseconds. A 4-inch telescope should split it at high power on a night of excellent, steady seeing. Also in the Moon's vicinity are Spica and Corvus.

    Sky at a Glance is now an iPhone app! Put S&T SkyWeek on your iPhone, iPad, or iPod Touch and get the above listings anytime, anywhere — with interactive sky maps! Tap a button to see the scene described, customized for your location worldwide. From there you can scroll the view all around the sky, zoom in or out, change to any time or date, and turn on animation.

    Go to Apple's iTunes store from your device to get S&T SkyWeek.

    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

    Saturn on April 5, 2011

    Saturn on April 5th, just past opposition. The rings are still brighter than usual compared to the globe due to the opposition effect (Seeliger effect); compare with past images (scroll down).

    The head of the northern-hemisphere white disturbance had barely crossed the central meridian when Christopher Go shot this image at 14:23 UT; the System III longitude on the central meridian was 222°. South is up.

    Note the faint dark spot on the B ring at lower right. Here's an animation of two exposures demonstrating that it's real. In the animation north is up, so look on the rings' left. Go asks, "Is this a spoke or a [satellite] shadow?" UPDATE: Here's another animation, from April 8th, clearly showing more spoke activity on the B ring.

    Christopher Go

    Mercury, Mars, and Jupiter are hidden in the glare of the Sun.

    Venus (magnitude –3.9) is still visible at dawn, but it's lower every week. Look for it low in the east-southeast as dawn brightens.

    Saturn (magnitude +0.4, in Virgo) is the lone planet in really good view. It's just past its April 3rd opposition. Look for it glowing low in the east-southeast as twilight fades. Saturn rises higher in the southeast during evening and shines highest in the south around midnight.

    Also during evening, look for twinkly Spica 12° below it or to its lower left, and brighter Arcturus 30° to its left.

    In a telescope, Saturn's rings are 9° from edge on. Saturn's months-old northern-hemisphere white spot has spread into a light band far around the planet, as seen above. See how many of Saturn's satellites you can identify in your scope using our Saturn's Moons tracker.

    Uranus and Neptune are low in the glow of dawn.

    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.

    To be sure to get the current Sky at a Glance, bookmark this URL:

    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.

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