Sky at a Glance | April 29th, 2011

Looking east in bright dawn
Before sunrise as April ends, the waning crescent Moon guides the way to four planets on the down-low. One should be easy to spot; the other three are a real challenge. (The visibility of the fainter objects in bright twilight is exaggerated here. 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.)

Friday, April 29

  • A dawn challenge: Set the alarm to get up and out Saturday morning well before your local sunrise time. Grab the binoculars or telescope, and be at a spot with a view of the eastern horizon by a half hour before sunrise. The waning crescent Moon will be low in the east. If the air is clear, Venus should be easy to pick up below it. Try next for Mercury 3° to Venus's lower left. Farther lower left is Jupiter. For a real challenge, tiny Mars is just 0.4° from Jupiter, as shown here.

    See our article on the whole next month of this dawn parade — with panels every day in an animation.

    Saturday, April 30

  • The big Coma Berenices Star Cluster is often hidden by light pollution. But if you're under a dark sky in springtime, be sure to look for it — a very large, dim speckly glow a third of the way from Denebola (the tail star of Leo) to the end of the Big Dipper's handle.

    Sunday, May 1

  • Arcturus is the brightest star in the east after dark. Saturn shines above Spica in the southeast. Look lower right of Saturn and Spica for the four-star springtime pattern of Corvus, the Crow.

    Monday, May 2

  • Now that May is here, at nightfall Vega has already risen low in the northeast (depending on your latitude). Above Vega is the four-star head of Draco, with its bright nose eternally pointed Vega-ward. Look for Draco's head about 1½ fists at arm's length above Vega and perhaps a bit left.

    Tuesday, May 3

  • Sirius in May?? You should still be able to spot the twinkling Dog Star low in the southwest as twilight fades. How much later into the warm season can you follow it down?

  • New Moon (exact at 2:51 a.m. EDT on this date).

    Twilight view
    Binoculars will help you pick out the Pleiades and Hyades when they're near or below the Moon. (The blue 10° scale is about the size of your fist held at arm's length. For clarity, the Moon is shown three times actual size.)

    Wednesday, May 4

  • Look low in the west-northwest at dusk for the thin crescent Moon with the Pleiades to its lower right (at the times of twilight for North America), as shown here. Orange Aldebaran is to the Moon's left.

    Thursday, May 5

  • The Moon at dusk poses (for North America) midway between Aldebaran below it and Beta Tauri above it.

  • The annual Eta Aquarid meteor shower should peak before dawn Friday morning. This is often the best shower of the year for Southern Hemisphere skywatchers, but in northern latitudes it's much weaker.

    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.

  • From Saturday morning until May 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. Farther right of the Moon is Capella. These four stars form an enormous arch over the lunar crescent at dusk. This is an archetypal springtime scene, repeated when the Moon is a waxing crescent each April and May.

    View in bright dawn, very low
    Four planets bunch up low in the dawn for more than a week to come. This is the arrangement on Sunday morning May 8th. Bring binoculars; their visibility in the brightening sky is exaggerated here.
    Sky & Telescope
  • The four planets low in the dawn are all becoming a little easier to see now. At right is the scene on Sunday morning.


    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).

    Pocket Sky Atlas
    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    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. Venus is the least low and by far the brightest. Use binoculars 20 or 30 minutes before sunrise to look below or lower left of Venus for much fainter Mercury. Look farther lower left of Venus for Jupiter. Jupiter is becoming a little higher and less difficult each morning. Mars, faintest of all, is near Jupiter; it passes 0.4° north (upper left) of the giant planet on the morning of May 1st.

    See our article on the whole next month of this dawn parade — with daily panels in an animation.

    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 +0.5, in Virgo) is the only planet in good view now. Look for it glowing in the southeast as the stars come out, with Spica twinkling to its lower left and bright Arcturus far to its left or upper left. Saturn rises higher after dark and shines highest in the south around 11 p.m. daylight saving time.

    In a telescope, Saturn's rings have narrowed slightly in the last few months to 8° from edge on. The pointlike source of Saturn's months-old white streak has rebrightened, as imaged here. And 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 1½° right or upper right of Saturn. It's 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 it during the coming weeks.

    Uranus is deep in the dawn.

    Neptune (magnitude 7.9, in Aquarius) is low in the east-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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