Earth--Day and Night Regions

Earth--Day and Night Regions

Planetary Positions

Sunday, March 25, 2012

Sky and Telescope: This Week's Sky at a Glance

This Week's Sky at a Glance

Some daily events in the changing sky for March 23 – 30

by Alan M. MacRobert

Dusk view
Watch the waxing crescent Moon march through its latest pairups with Jupiter and Venus. (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. For clarity, the Moon is shown three times actual size.)
Friday, March 23

  • Venus and Jupiter continue shining in the west during and after dusk this week, though ever farther apart. Venus is so bright that it's easy to spot before sunset if you have normally sharp vision. About a half hour after sunset this evening, look very far below Venus and Jupiter, and perhaps a little right, for the very thin, day-and-a-half-old crescent Moon as shown here.
    Saturday, March 24

  • Venus, Jupiter, and the crescent Moon now form a flattened triangle in the west as twilight fades. As darkness deepens, look above Venus for the Pleiades.
    Sunday, March 25

  • The Moon hangs with Jupiter this evening, as shown here. Consider this a warmup for its pairing with brighter Venus tomorrow. It's also a good opportunity to see Jupiter even before the Sun sets — something that's possible but rarely done with the unaided eye.
    Monday, March 26

  • The Moon and Venus, the two brightest celestial objects after the Sun, appear paired up in the west this evening. In reality Venus is 260 times farther away. It's at a distance of 6 light-minutes from Earth, compared to the Moon's distance of 1.3 light-seconds. Jupiter, looking on from below, is currently 48 light-minutes from Earth.
    Coincidentally, Venus is at its greatest elongation: 46° east of the Sun. That makes this the very best possible time to spot Venus during daylight hours.
    Tuesday, March 27

  • As night comes on, look for the little Pleiades cluster to the lower right of the Moon and above Venus. Left of the Moon shines orange Aldebaran, with the stars of the Hyades around it.

  • Early Wednesday morning, along a path from New Mexico to central California, the 6.8-magnitude star 14 Virginis will be occulted low in the west-southwestern sky by the small asteroid 823 Sisigambis. The star should vanish for no more than 1.6 seconds within several minutes of 11:23 Universal Time.Charts and details.
    Wednesday, March 28

  • If you observe with binoculars you're probably well acquainted with the big Beehive Cluster, M44 in Cancer, very high in the evening this month. But how about the smaller, fainter cluster M67 in the same vicinity? And have you tried to resolve Iota Cancri, a rather difficult binocular double star? See Gary Seronik's Binocular Highlight column and chart in the March Sky & Telescope, page 45.

  • The eclipsing variable star Algol should be at minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 9:00 p.m. EDT.
    Thursday, March 29

  • This is the time of year when the dim Little Dipper juts to the right from Polaris (its handle-end) during evening hours. The much brighter Big Dipper curls over high above it, "dumping water" into it.

  • This is also the time of year when Orion, declining in the southwest after dark, displays his three-star Belt more or less horizontally.
    Friday, March 30

  • First-quarter Moon (exact at 3:41 p.m. EDT). The Moon shines in the legs of Gemini, below Pollux and Castor and high above sinking Betelgeuse.
    Saturday, March 31

  • The Moon shines high in the southwest this evening. It forms a gently curving line (as seen from North America) with Pollux and Castor to its upper right and Procyon below it.

    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 Astronomybooklet (which only has bimonthly maps).
    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 are less than top-quality mechanically (able to point with better than 0.2° repeatability). 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 is hidden deep in the glow of sunrise.
    Venus and Jupiter are moving apart now but still form a spectacular pair in the western evening sky. They're 9° apart on March 23th and 14&@176; apart by the 30th. Venus is the brighter one, on top. It will stay about the same height at dusk well into April, but Jupiter is sinking ever lower. These are the two brightest celestial objects after the Sun and Moon, being magnitudes –4.5 and –2.1 right now, respectively.
    Venus is at greatest elongation this week (exact on March 26th). For skywatchers at mid-northern latitudes, this is Venus's highest showing in its 8-year cycle of apparitions.
    In a telescope Venus is now a bit less than half lit and 23 arcseconds tall. Jupiter shows a much lower surface brightness, being farther from the Sun, but its apparent diameter is somewhat larger: 32″ (though this is small for Jupiter).
    Mars (magnitude –0.9) shines bright fire-orange under the belly of Leo. Fainter Regulus is 6° or 7° to its upper right in early evening, and Gamma Leonis is farther above it.
    Mars was at opposition on March 3rd. Now it's fading and shrinking a bit as Earth pulls ahead of it along our faster, inside-track orbit around the Sun. But at least Mars is shining higher in the evening sky now, reaching a good altitude for telescopic observing at a convenient hour. It's highest in the south by around 11 p.m. daylight-saving time.
    In a telescope Mars is 13.0 arcseconds wide. It won't appear this big and close again until 2014. Notice the much shrunken little North Polar Cap; spring is giving way to summer in Mars's northern hemisphere. See our Mars map and observing guide in the April Sky & Telescope, page 50.
    Saturn (magnitude +0.3, in Virgo) rises in the east around the end of twilight and glows highest in the south around 2 a.m. Shining 6° to its right is Spica, about half as bright at magnitude +1.0 and bluer. In a telescope Saturn's rings are tilted 14° from our line of sight.
    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 Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.

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