Sky at a Glance | February 29th, 2008

By: Alan MacRobert February 29, 2008 0

Some daily events in the changing sky for February 29 – March 8.

If you're up early, look low in the brightening dawn for every significant object in the solar system that's currently closer to the Sun than Earth is. Plus Jupiter. (These scenes are drawn for the middle of North America. Southerners will see all the objects higher. 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.)

Sky & Telescope illustration

Friday, February 29

Right at nightfall this week, Orion stands perfectly erect with his two feet-stars (Rigel and Saiph) perfectly level. High above him glows little Mars. Off to his left, by about two fist-widths at arm's length, is Procyon, the Little Dog Star, following behind him as he crosses the sky. Lower left of Orion by a similar distance is brighter Sirius, the Big Dog Star, trotting behind too.

Saturday, March 1

As twilight fades and the stars come out, look straight overhead for bright Capella. If you happen to live at latitude 46° north (the Oregon-Washington border, Montreal, central Maine, central France), Capella passes exactly over your head once a day. If you're south of there, Capella passes 1° north of your zenith for every degree you're south of that latitude. At this time of year, it happens just when evening twilight fades enough for bright stars to become easily visible.

Sunday, March 2

With no Moon in the evening sky this week, 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 running through the constellations of the zodiac. What you're seeing is interplanetary dust in the plane of the solar system, lit by sunlight.

This is the best season of the year for seeing the evening zodiacal light if you're in the Northern Hemisphere — because this is when the ecliptic extends most nearly upright from the western horizon at dusk.

Monday, March 3

Low in the dawn tomorrow morning, the waning crescent Moon points the way to Venus and Mercury, as shown above.

Tuesday, March 4

The thin crescent Moon is close to Venus and Mercury very low in the southeast as dawn brightens Wednesday morning, as shown above. Bring binoculars.

In daylight on June 18, 2007, Alan C. Tough in Scotland took this shot of Venus just before it was occulted by the dark limb of a thin waxing Moon. The Moon was much thicker (15% illuminated) and farther from the Sun than it will be on March 5th. Tough used a Canon EOS 300D camera with a 600-mm lens. Exposure: 1/320th second, f/6.3, ISO 100. Click image for larger view.

Alan C. Tough

Wednesday, March 5

The thin waning crescent Moon occults (covers) Venus during daylight today for central and western North America and Mexico. The little planet will disappear behind the Moon's ghostly edge in a bright sky only 25° from the Sun, so this will be quite a tough sighting even with a telescope. See our article (with link to local timetables).

Thursday, March 6

Little Mars isn't much for telescopes anymore, now that it's fading into the distance. But it's entering Gemini, a constellation rich with telescopic treasures. Instead of just moping over Mars, check out some objects that you've never heard of — using Sue French's "Deep-Sky Wonders" column and chart in the March Sky & Telescope, page 74.

Friday, March 7

As the stars come out this week, the Big Dipper is high in the northeast balancing upright on its handle. As night advances, the Dipper climbs higher and tips leftward. Look far down to its lower right for bright Arcturus, the "Spring Star," rising in the east. Arcturus is a little more than a Dipper-length from the end of the Dipper's handle.

New Moon (exact at 12:14 p.m. EST).

Saturday, March 8

Daylight Saving Time begins for most of North America at 2 a.m. Sunday morning. Clocks "spring ahead" an hour. Be sure to make this change in our online almanac if you use it (check the Daylight Saving Time box). Daylight time for North America now runs from the second Sunday in March to the first Sunday in November; the rules changed in 2007. Daylight time is not used in Hawaii, Saskatchewan, Puerto Rico, or in most of Arizona.

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 foldout 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).

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of maps; 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 enchanting though increasingly dated Burnham's Celestial Handbook). Read how to use them effectively.

More beginners' tips: "How to Start Right in Astronomy".

This Week's Planet Roundup

Mars is now a featureless little gibbous blob in most telescopes, but Sean Walker recorded its major features well on the evening of March 2nd using a 12.5-inch scope, stacked video frames, and some fairly intense image processing. North is up. Syrtis Major pokes upward on the right, and Sinus Sabaeus runs leftward to Sinus Meridiani on the sunrise terminator. Mars was just 8.9 arcseconds in diameter at the time. The central-meridian longitude was 320°.

S&T: Sean Walker

Mercury (about magnitude +0.0) is just 2° or 3° to the upper right of brilliant Venus low before sunrise. But it's dozens of times fainter, so bring binoculars.

Venus (magnitude –3.9, in Capricornus) is getting lower every morning. Look for it above the southeast horizon about 30 minutes before sunrise, far lower left of Jupiter.

Mars (about magnitude +0.3, at the Taurus-Gemini border) shines very high in the south to southwest during evening, high over Orion. In the same binocular field of view with Mars is the star cluster M35 in Gemini. In a telescope this week, Mars dwindles from 9.1 to 8.4 arcseconds wide — pretty tiny.

Jupiter (magnitude –2.0, in Sagittarius) shines low in the southeast before and during dawn. It's moving ever farther to the upper right of Venus.

Saturn's rings are currently tilted only 8° to our line of sight, as seen in this image taken on the evening of February 23rd when Saturn was at opposition. Two weeks earlier, the outer edge of the rings was sharply outlined by a thin line of their black shadow on the globe, but now the shadow is hidden. Note the dusky C ring just inside the broad, bright B ring. The C ring is obvious as a dark silhouette where it crosses in front of the globe. North is up.

S&T: Sean Walker

Saturn (magnitude +0.2, in Leo) was at opposition on February 23rd. It glows low in the east as twilight fades, rises higher all evening, and stands highest in the south around 11 p.m.

Fainter Regulus (magnitude +1.4) is 5° west of Saturn: to its upper right in early evening, and directly right of it later. Only a little dimmer than Regulus is Gamma (γ) Leonis (magnitude +2.1), located 8° more or less to Regulus's north. The three make an eye-catching triangle. Watch the triangle narrow in the coming weeks.

Uranus and Neptune are hidden in the glare of the Sun. (Neptune is in the vicinity of Venus and Mercury, but it's too dim to see through the bright dawn even with a telescope.)

Pluto (magnitude 14.0, in Sagittarius) is in the southeast before dawn's first light.

Dennis di Cicco shot this image of Comet Holmes using a Tele Vue NP127is (5-inch) refractor and Apogee Alta camera on February 11th. The field is 3° tall, with north up. "This comet is getting huge!" he writes. "So much so that I initially had a difficult time seeing it in a short exposure, because it looked like the typical 'hot spot' in the center of the frame due to optical vignetting." Click image for larger view.

S&T: Dennis di Cicco

Comet Holmes is passing the California Nebula this week. Both are dim but large. Think photo opportunity!

The comet itself continues to dim. On February 11th through suburban light pollution, Dennis di Cicco could not see it with the naked eye at all when he took the picture at right.

On February 24th, says Tony Flanders, "the comet was barely visible naked-eye from a modestly dark rural site. It was still pretty obvious in 15x70 binoculars, and it looked to me to be about 1° by 3/4°. I could see no sign of internal detail at all." Holmes is now shrinking slightly in apparent size as it moves farther from Earth and, also, as its outermost parts fade to invisibility.

The comet continues moving eastward in Perseus; look as soon as nightfall is complete. Chart.

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 (UT, UTC, or GMT) minus 5 hours. Eastern Daylight Time (EDT) is UT minus 4 hours.

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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.