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This Week's Sky at a Glance

Some daily sky sights for May 4 – 12

by Alan M. MacRobert

The Moon shines below Saturn and Spica as the stars come out on May 4th and 5th. The blue 10° scale is about the size of your fist at arm's length.
Sky & Telescope diagram
Friday, May 4

  • Look above the bright Moon this evening for Saturn and Spica, as shown here.

    Saturday, May 5

  • Full Moon (exact at 11:35 p.m. EDT), in Libra. This is the closest and largest full Moon of 2012, though not remarkably so. The Moon is 8% closer and larger than average, and only 0.16 magnitude brighter than average, so you'd need measuring tools to really tell. Take a look. What do you think?

    Sunday, May 6

  • Venus, the brilliant "Evening Star" in the west, is passing its closest to the star Beta Tauri, which is only 1/300 as bright at magnitude 1.6. During and after late twilight, look for the star 0.8° to Venus's upper right. That's about a pencil-width at arm's length.

    Although they look close together, they're not. Venus is 3 light-minutes from us; Beta Tauri is 130 light-years in the background.

    Monday, May 7

  • The waning gibbous Moon is up in the southeast by around 11 p.m., depending on where you live. Look about a fist-width to the Moon's right for fiery Antares. Around and upper right of Antares are other stars of Scorpius.

    Tuesday, May 8

  • The brightest star very high in the east these evenings is Arcturus. Look three fist-widths to its lower right for Saturn and, a little farther on, Spica.

    Wednesday, May 9

  • Look for bright Vega moderately low in the northeast after darkness falls, and higher later. To Vega's lower right dangle fainter stars of the little constellation Lyra.

    Thursday, May 10

  • For deep-sky observers, a favorite springtime telescopic star-hop runs from the end of the Big Dipper's handle to the Whirlpool Galaxy, M51, and on to the Sunflower Galaxy, M63. Did you know there's a red semiregular variable star to check out along the way? See the May Sky & Telescope, page 53.

    Friday, May 11

  • Bright Venus has been dropping lower in the west-northwest every evening. To its right is the much fainter star Beta Tauri. They're now 1½° apart.

    Saturday, May 12

  • Last-quarter Moon (exact at 5:47 p.m. Eastern Daylight Time). The Moon rises in the middle of the night, looking lopsided and awkward in dim Aquarius.




    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, Deluxe Edition
    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.
    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 the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger 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 Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? I don't think so — not for beginners, anyway, and especially not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability). As Terence Dickinson and Alan Dyer say in their invaluable 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 is lost deep in the glow of sunrise.

    Venus (magnitude –4.7, in Taurus) is the blazing "Evening Star" high in the west in twilight, and lower later in the evening. It's still as bright as it ever gets, but it's beginning its rapid May descent toward the sunset. See article, Venus Takes the Plunge.

    Look high to Venus's upper right for Capella. Look very close to the bright planet for Beta Tauri, also known as El Nath, glimmering only 1/300 as bright (at magnitude +1.6). Beta Tauri is 1° above Venus on May 4th, 0.8° to Venus's upper right when they're closest together on the 6th, and 1.6° to the planet's right by May 11th.

    You can see Venus through the clear blue sky of day if your eye lands right on it. Look for it 35° (three or four fist-widths at arm's length) to the celestial east of the Sun.

    The best time to examine Venus in a telescope is late afternoon or around sundown. It's now a crescent about 42 arcseconds tall and 20% sunlit, waning and enlarging daily. Venus will transit the face of the Sun on June 5–6 (on the afternoon of the 5th for North America); see our article in the June Sky & Telescope, page 50, or online. This is the last transit of Venus until 2117.

    Mars on April 22, 2012
    Mars was only 10.8 arcseconds wide on the evening of April 22nd, when Sean Walker shot this stacked-video image using his 12.5-inch reflector in New Hampshire. South is up. Note the divided little North Polar Cap, and the bright clouds over Tharsis at the preceding limb (left).
    S&T: Sean Walker
    Mars (magnitude +0.1) shines fire-orange in Leo. It's high in the south-southwest at dusk and lower in the southwest to west later in the evening.

    Regulus is about 7° Mars's right or lower right and moving farther from it daily. Fainter Gamma Leonis is 8° above Regulus.

    Mars in a telescope is gibbous and small, about 9.5 arcseconds wide, fading and shrinking each week.

    Jupiter is lost in the glare of the Sun.

    Saturn (magnitude +0.4, in Virgo) shines in the southeast in twilight and highest in the south around 11 or midnight daylight saving time. The star 5° to Saturn's lower right in the evening is Spica, slightly fainter and bluer.

    Uranus is very low in the dawn.

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