Sky at a Glance | February 13th, 2009

Some daily events in the changing sky for February 13 – 21.

Comet Lulin is once again in a dark, moonless sky starting late on the night of the 15th or 16th. Using binoculars or a telescope, look for it high around midnight or 1 a.m. The comet is moving rapidly westward across Virgo this week at about magnitude 5.5 or 6. Its peak brightness should come around February 24th. Full story and finder charts.


Friday, February 13

  • Mercury is at greatest elongation, 26° west of the Sun low in the dawn.

    Saturday, February 14

  • Happy Lupercalia Valentine's Day. Becky's Infinity Heart, in southern Sagittarius and Corona Australis (look left of the drawing in the link), is just emerging into view before dawn, at least for Valentine's Day observers the tropics and the Southern Hemisphere.

    Sunday, February 15

  • Comet Lulin is 3° north of Spica early Monday morning — just as a two-week window of moonless observing time is opening up for it. The comet will be best seen with binoculars shortly before moonrise, around midnight or later tonight. Find your moonrise time using our online almanac (make sure the Daylight Saving Time box is unchecked).

    Anticipating the spot where the dazzling Sun will soon burst into view, Mercury, Jupiter, and Mars glimmer low in bright dawn. Bring binoculars; their brightnesses here are exaggerated.
  • Before sunrise tomorrow, Jupiter and faint Mars are close together and lined up horizontally well to the lower left of Mercury, as shown at right. Their brightnesses in these diagrams are exaggerated; bring binoculars.

    Monday, February 16

  • Last-quarter Moon (exact at 4:27 p.m. EST).

  • On Tuesday morning the 17th, tiny Mars is 0.6° south (lower right) of Jupiter very low in bright dawn.

    Tuesday, February 17

  • With the evening sky moonless this week, it's a fine time to look for the zodiacal light as twilight fades out. You'll need a clean, unpolluted sky. The zodiacal light is a huge, narrow, tilted pyramid of pearly glow extending up from the western horizon and tilting to the left, running through the constellations of the zodiac. What you're seeing is interplanetary dust in the plane of the solar system, lit by sunlight. At this time of year, the western-sky ecliptic after dusk, and therefore the zodiacal light, is tilted high.

    Wednesday, February 18

  • The red long-period variable star V Cassiopeiae should be near maximum light (8th magnitude) around now.

    Thursday, February 19

  • Venus displays its greatest illuminated extent (its greatest number of sunlit square arcseconds).

  • A small telescope will always show Titan, Saturn's largest moon. Tonight and tomorrow night Titan is four ring-lengths to Saturn's east. A 6-inch telescope will show the orange color of its smoggy atmosphere. A guide to identifying all six of Saturn's satellites that are sometimes visible in amateur scopes is in the February Sky & Telescope, page 57.

    The waning crescent Moon joins the dawn challenge sightings on Saturday and Sunday mornings, Feb. 21 and 22. It will almost certainly be too low by the 23rd. (The Moon's positions are for North America.)
    Friday, February 20

  • This is the time of year when Orion stands at his highest due south after dinnertime, around 7 or 8 p.m. So this is when your scope may do its best in revealing detail in the Great Orion Nebula — and in particular, if the seeing is very steady, the difficult fifth and sixth stars (stars "E" and "F") of the Trapezium multiple star in the nebula's heart (see photo and chart; scroll down).

    Saturday, February 21

  • Go out a half hour before Sunday's sunrise if the sky is clear, look low in the east-southeast with binoculars, and you'll be rewarded with a diagonal lineup of the crescent Moon, Mercury, Jupiter, and maybe even faint Mars, as shown at right.


    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 81,000 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 — 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 even more detailed 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? 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

    Jupiter, Mercury, and Mars (magnitudes –1.9, 0.0, and +1.2, respectively), are low in the glow of sunrise, where they're changing configuration daily. They start the week with Jupiter and tiny Mars close together well to Mercury's lower left; Mercury moves in on them day by day. Bring binoculars and look just above the east-southeast horizon about 30 minutes before sunup.

    (Find your local sunrise time by making sure you've put your location into our online almanac, and make sure the Daylight Saving Time box is unchecked.)

    Venus (magnitude –4.8, in Pisces) is the dazzling "Evening Star" high in the west during and after twilight. It's at its peak brightness now, and it doesn't set until about 9 p.m. In a telescope Venus is a thick crescent (31% sunlit) about 37 arcseconds from cusp to cusp. Telescopically, Venus is best seen in bright twilight or even broad daylight; it's less glary against a bright sky, and it's usually higher.

    Ceres resolved with an 11-inch scope!
    Ceres was near its closest opposition of our lifetimes, and 0.83 arcseconds wide, when John Sussenbach of Houten, Netherlands, resolved its disk by video imaging Feb. 14, 2009. At right is a star's diffraction pattern imaged for comparison. He used a Celestron 11-inch Schmidt-Cassegrain scope with a 3× Barlow, a DMK2AF4.AS video camera, and RGB filters. In each color he took 980 frames and used Registax 4.0 to select and stack the best 500 from each. Click image for more.
    Ceres (magnitude 6.9, in Leo), is having its best apparition of our lifetime. This "dwarf planet," the largest of the main-belt asteroids, will be at opposition next week. See the article and chart in the March Sky & Telescope, page 60.

    Saturn (magnitude +0.6) remains near the hind foot of Leo, the 4th-magnitude star Sigma Leonis. Saturn rises around 7 p.m., shines well up in the east by 9 or 10, and is highest in the south around 1 a.m. Don't confuse it with similarly-bright Regulus 20° (two fist-widths at arm's length) to its upper right after they rise, and more directly to its right in the early-morning hours.

    Notice that Saturn is pale yellow and shines with a steady light, while Regulus is white with a touch of blue and (unless the air is very steady) twinkles slightly.

    Titan was leaving Saturn's face when Christopher Go in the Philippines took these images 10 and 12 minutes apart starting at 18:00 UT February 8th. As you can see, Titan's murky orange atmosphere is darker than Saturn's bright cloudtops. (The dark ring around Titan in the first frame is an image-processing artifact.) North is up. Click image to see an animation.


    P.S.: Here are the times and dates (in UT) of all of Titan's transits, and transits of its shadow, across Saturn in 2009.

    This week Saturn's rings are 1.8° from edge on. The rings will gradually open to 4° by late May, then will close to exactly edge-on early next September — when, unfortunately, Saturn will be out of sight practically in conjunction with the Sun.

    Uranus and Neptune are lost behind the glow of the Sun.

    Pluto is low in the southeast before dawn.

    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 Standard Time (EST) equals Universal Time (known as UT, UTC, or GMT) minus 5 hours.


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