Friday, May 14

  • In early twilight, use binoculars to look for the very young crescent Moon just above the west-northwest horizon. It's far lower right of Venus, as shown below. Having found it with binoculars, can you pick it up with the naked eye? If you see the Moon before 9:04 p.m. Eastern Daylight Time (regardless of your time zone), you've spotted it when it's less than 24 hours old; new Moon was at 9:04 p.m. EDT on May 13th.
  • Venus itself, meanwhile, shines just about midway between the horn-tip stars of Taurus: Beta (β) and Zeta Tauri. Beta is the brighter one, at Venus's right.

    Twilight view

    Watch the Moon passing Venus in twilight. These diagrams are drawn for the middle of North America. European skywatchers: move each Moon symbol a quarter of the way to the one for the previous date. The visibility of faint objects in bright twilight is exaggerated here.

    Sky & Telescope diagram


    Saturday, May 15

  • As twilight deepens, the thin crescent Moon hangs to the lower right of Venus in the west. And Venus itself has now moved off the line from Beta to Zeta Tauri, as is shown above.

    Sunday, May 16

  • This evening the thickening crescent Moon shines to Venus's upper left, as shown above. The faint orange stars near it, as twilight deepens into night, are in the feet of Gemini.

    Monday, May 17

  • It's May, so the Big Dipper floats upside down high overhead when you face north as the stars come out. Turn around to face southwest; there stands Leo, with yellow-gold Mars to its right and yellow-white Saturn to its left.

    Tuesday, May 18

  • May flowers mean May galaxies! For two telescopic guided tours, see Sue French's Deep-Sky Wonders column and Ken Hewitt-White's more ambitious Going Deep column in the May Sky & Telescope, pages 65 and 68.

    Moon, Mars, and Regulus

    The Moon passes under Mars and Regulus on Wednesday and Thursday nights.

    Sky & Telescope diagram


    Wednesday, May 19

  • Mars is about 6° above the Moon this evening (for North America), as shown at right.

    Thursday, May 20

  • Regulus is about 5° upper right of the first-quarter Moon this evening (for North America), as shown at right. The Moon is exactly first quarter at 7:43 p.m. EDT.
  • A telescope shows Titan at greatest elongation from Saturn tonight and tomorrow, about four ring-lengths to the planet's west. Titan swings around Saturn every 16 days.

    Friday, May 21

  • As dusk fades into night, turn binoculars or a telescope on dazzling Venus in the west-northwest. Look less than 1° lower left of Venus for the big open star cluster M35.

    Saturday, May 22

  • The "star" above the gibbous Moon this evening (by about 8°: as seen from North America) is Saturn. The much fainter star about 2° to Saturn's lower right this week is Beta Virginis.

    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.

    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


    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

    Jupiter on May 6, 2010

    Jupiter's dark North Equatorial Belt is currently wide and massive, in contrast to the almost nonexistent South Equatorial Belt — whose absence leaves the Great Red Spot floating free in whiteness. Note too "Red Spot Junior" (Oval BA) adding a trace of color near the upper right limb. South is up.

    Christopher Go in the Philippines took this image on May 6th at 20:42 UT, when the central-meridian longitude was 156° (System II). The 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.

    Christopher Go


    Mercury is having a poor apparition low in the dawn.

    Venus (magnitude –3.9, moving from Taurus to Gemini) is the bright Evening Star shining in the west-northwest during and after twilight. Capella is the bright star far to its upper right. On Friday the 14th Venus poses midway between Taurus's horn-tips, Beta and Zeta Tauri. After that, these two stars slide away to Venus's lower right.

    Mars (magnitude +0.9, in Cancer) is high in the west during evening, very far upper left of Venus along the ecliptic. Mars is moving eastward against the stars; week by week it's closing in on Regulus to its upper left. They'll pass each other on June 6th, 0.8° apart.

    In a telescope Mars is just a tiny blob, 6.6 arcseconds in diameter. Can you still make out its gibbous shape? Mars is as gibbous as it will appear all year, with only 90% of its diameter sunlit.

    The other side of Jupiter (CM II longitude 4°), imaged by Go on May 17th. South is up. He writes: "There is a huge rift in the North Equatorial Belt (NEB). Something seems to be stirring up this region." Also, "The SEB is very pale. Note that the mid-SEB is a bit bluish. Note the white ovals on the SSTB. There are two white ovals on top of each other."

    Christopher Go


    Jupiter (magnitude –2.2, below the Circlet of Pisces) shines in the east-southeast at the first light of dawn. Nothing else there is nearly so bright.

    Saturn (magnitude +0.9, in the head of Virgo) is high in the southwest during evening. In a telescope Saturn's rings are tilted a mere 1.7° from edge-on, their minimum tilt for the next 15 years. They'll stay this narrow for the next month. Note the thin black shadow-line that they cast on Saturn's globe. The line is thicker and more prominent now than it was a few weeks ago.

    Uranus (magnitude 5.9, in Pisces) is in the background of Jupiter at the crack of dawn.

    Saturn and SED on May 10, 2010

    As of May 10th the Saturn Electrostatic Disturbance (SED) white spot was back yet again. This ammonia-blizzard thunderstorm is a very difficult eyeball sighting even in a large amateur telescope, but amateur stacked-video imagery like this is showing it again plainly. Amateurs have been creating a good record of the SED's brightenings and dispersals in the last few months.

    South is up in this image taken May 10, 2010, at 11:21 UT, by Anthony Wesley in Australia. Click for his full-size images. The System III central-meridian longitude was 51°. The spot has been moving nearly 1° per day toward increasing System III longitudes since amateurs began imaging it two months ago.

    Anthony Wesley


    Neptune (magnitude 7.9, at the Aquarius-Capricornus border) is in view just before dawn well to Jupiter's west (upper right). See our finder charts for Uranus and Neptune in 2010.

    Pluto (magnitude 14, in northwestern Sagittarius) is highest in the south before dawn. 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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