Sky at a Glance | May 1st, 2009

Some daily events in the changing sky for May 1 – 9.

Friday, May 1

  • First-quarter Moon (exact at 4:44 p.m. EDT).

    The Moon shines under Regulus on May 2nd and Saturn on May 3rd. These scenes are always 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. In the Far East, move it halfway. (For clarity, the Moon is shown three times actual size.)
    Saturday, May 2

  • The Moon shines about 3° below Regulus during evening for North America, as shown at right.

  • A small telescope will nearly always show Titan, Saturn's largest moon. Tonight and tomorrow Titan is four ring-lengths to Saturn's west. A guide to identifying other Saturnian satellites visible in amateur scopes is in the May Sky & Telescope, page 47.

  • Venus in the morning sky is at its greatest illuminated extent: its sunlit area appears largest as seen in a telescope (that is, it covers the most square arcseconds). This is very close to when Venus is at its greatest brilliancy.

    Sunday, May 3

  • This evening the Moon shines below Saturn, as shown at right. Although they look close together, Saturn is currently 3,500 times farther away. And Regulus is 560,000 times farther than Saturn!

    Monday, May 4

  • Irene and Flora, two springtime asteroids, are a little past opposition this week. At 9th and 10th magnitude they await your telescope, and your chart-using skills, as they drift only about 4° apart between the legs of Virgo. See the article and the 10th-magnitude chart in the May Sky & Telescope, page 46.

    Venus is only about 5° from faint Mars low in the eastern dawn all this week. (The visibility of Mars in bright twilight is exaggerated here.)
    Tuesday, May 5

  • The Eta Aquarid meteor shower should be at its peak before the first light of dawn Wednesday morning, though the shower runs for a few days before and after too. This is often the best annual meteor shower for the Southern Hemisphere. Few of its meteors, however, are visible from mid-northern latitudes. On Wednesday morning, far-southerners get about an hour's window of darkness after moonset and before dawn's first light.

    Wednesday, May 6

  • Look to the Moon's upper left this evening for Spica, in Virgo. Farther right of the Moon is the constellation Corvus. Way, way off to the Moon's upper left is brighter Arcturus.

    Thursday, May 7

  • Sometime around 10:00 p.m. daylight saving time, bright Vega in the northeast and bright Capella in the northwest will be at exactly the same height. The moment when this balance occurs depends on your location in your time zone, especially how far east or west you are. How accurately can you time this event at your site?

    Friday, May 8

  • Full Moon tonight (exact at 12:01 a.m. Saturday morning Eastern Daylight Time).

    Saturday, May 9

  • By 11 p.m. the Moon is well up in the southeast. Look to its lower left, by a bit less than a fist-width at arm's length, for the reddish summer star Antares on the rise. Scattered nearby are fainter stars of Scorpius.


    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 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'll need a detailed, large-scale sky atlas (set of charts; the standards are
    Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.

    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 and a curious mind." Without these, they note, "the sky never becomes a friendly place."

    More beginners' tips: "How to Start Right in Astronomy".


    This Week's Planet Roundup

    Facing west-northwest 60 minutes after sunset
    By May 1st and 2nd, the Pleiades slide down to pose directly to Mercury's right. Don't confuse Mercury with Aldebaran, a little higher.
    Mercury fades rapidly this week (from magnitude +1 to +3) and starts dropping down into the sunset. Look for it early in the week low in the west-northwest about an hour after sunset. As darkness deepens, look for the Pleiades just to its right, as shown here.

    Venus (magnitude –4.7) shines brightly low in the east during dawn. Don't confuse it with Jupiter, higher and far to the right in the southeast. In a telescope, Venus is a thickening and shrinking crescent. The best telescopic views come in full early-morning daylight, when Venus is higher in steadier air.

    Mars (only magnitude +1.2) remains 5° or 6° lower left of Venus all week. Bring binoculars; Mars is 230 times fainter than Venus! Mars is beginning a long, slow apparition that will bring it to opposition on January 29, 2010.

    Jupiter (magnitude –2.2, in Capricornus) shines brightly in the southeast before and during dawn.

    Saturn (magnitude +0.8, in Leo) is highest in the south in early evening and moves to the southwest later. Regulus, not quite as bright, sparkles 15° to its right at dusk, and to its lower right later.

    Saturn on the evening of April 29th, imaged through poor seeing by Sean Walker.
    S&T: Sean Walker
    In a telescope, Saturn's rings appear 4° from edge on, their widest this year. They'll close to exactly edge-on September 4th, when, unfortunately, Saturn will be out of sight practically in conjunction with the Sun.

    Uranus (6th magnitude) is low in the sunrise glow, in the background of Venus — and 17,000 times fainter.

    Neptune (8th magnitude) is the background of Jupiter — and 11,000 times fainter.

    Pluto (14th magnitude, in northwestern Sagittarius) is highest in the south before the first light of dawn. It's 250 times fainter than even Neptune.

    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.


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