Sky at a Glance | March 18th, 2011

Friday, March 18

  • By mid-evening, look far to the lower left of the Moon for Saturn and, below it, twinkly Spica on the rise. Far to their left sparkles brighter Arcturus, the "Spring Star."

    Late-evening view
    The big bright Moon guides the way to Saturn and its springtime surroundings.
    Alan MacRobert

    Saturday, March 19

  • Full Moon (exact at 2:10 p.m. Eastern Daylight Time). The Moon is in Virgo, along with Saturn and Spica as shown at right. The Moon is at perigee, and this is a slightly closer perigee than usual. So the Moon will appear bigger and brighter than it has in 19 years — but only by a slight trace!

    Sunday, March 20

  • Spica is near the Moon tonight.

  • The March equinox comes at 7:21 p.m. EDT, marking the start of spring in the Northern Hemisphere. This is when the Sun crosses the equator heading north for the year.

    Monday, March 21

  • Mercury is at its highest in the evening sky from now until Wednesday. Use our article to locate Mercury a half hour after sunset.

    Tuesday, March 22

  • These next two weeks, when there's no moonlight in the sky at the end of twilight, are a fine time to look for the zodiacal light (from mid-northern latitudes) if you have a very clear, unpolluted sky. As the last of twilight is fading away, look for a vague but huge, tall, narrow pyramid of pearly light extending up from the western horizon. It slopes to the left, following the ecliptic. What you're seeing is interplanetary dust near the plane of the solar system, lit by the Sun.

    Early-spring Orion
    Orion, with belt horizontal, was declining in the southwest when S&T's Tony Flanders took this 15-second exposure with a Canon A80 pocket digital camera.
    Tony Flanders

    Wednesday, March 23

  • By midevening Orion is tilting into the southwest, with his three-star belt now level — a sign of spring's arrival.

    Thursday, March 24

  • If you've got a telescope, you've probably looked at the Great Orion Nebula many times this season. So it's time to branch out before Orion goes away for the spring. Right after dark, hunt out little-known clusters and nebulae spotlighted and charted in Sue French's article "Oddities in Northern Orion" in the March Sky & Telescope, page 64.

  • Algol, in Perseus in the northwestern sky, is at its minimum brightness (magnitude 3.4 instead of its usual 2.1) for a couple hours centered on 8:38 p.m. Pacific Daylight Time.

    Friday, March 25

  • A binocular challenge: See it you can hunt out the trio of Messier galaxies under the belly of Leo: M95, M96, and M105. Use Gary Seronik's "Binocular Highlight" article and chart in the April Sky & Telescope, page 45. You'll need a really dark sky! A telescope shows them much more easily.

    Saturday, March 26

  • Last-quarter Moon (exact at 8:07 a.m. EDT). The half-lit Moon rises in the middle of the night and is high in the south before sunrise.



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    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 at Its Evening Highest for 2011
    After passing Mercury last week, Jupiter now descends toward the sunset horizon day by day. Their visibility in bright twilight is exaggerated here.

    Mercury (about magnitude 0) is having its best apparition of 2011 in the western twilight. Jupiter is sinking ever lower below it.

    Venus (magnitude –4.0) shines low in the southeast during dawn, lower each week.

    Mars is out of sight behind the glare of the Sun.

    Jupiter (magnitude –2.1) sinks very low in the west in bright twilight. Look for it below well Mercury.

    Saturn (magnitude +0.4, in Virgo) rises around 8 p.m., but it's best seen in a telescope much later in the night when it gains high altitude. It's highest in the south around 2 a.m. daylight saving time. Spica, slightly fainter, shines about 10° below Saturn all evening.

    Saturn on Feb. 11, 2011
    By February 11th Saturn's white spot had become a patchy band. Part of the dark, reddish South Equatorial Belt can be seen just south of (above) the rings.

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

    Uranus and Neptune are hidden in the sunrise.


    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 Standard Time (EST) equals Universal Time (also known as UT, UTC, or GMT) minus 5 hours. Eastern Daylight Time (EDT) is UT minus 4 hours.


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