Some daily events in the changing sky for January 29 – February 6.

Mars and Moon, both at opposition

Two worlds at opposition, as seen in the east-northeast in twilight.

Sky & Telescope diagram


Friday, January 29

  • Mars is at opposition, opposite the Sun in Earth's sky. So is the full Moon next to it! Moreover, the Moon is at perigee, making this the largest and brightest full Moon, by a little bit, of the year.
  • Once Saturn rises into good view late tonight, a small scope will show its largest satellite, Titan, about four ring-lengths to the planet's west.

    Saturday, January 30

  • Mars shines above the Moon this evening, by about 1½ fist-widths at arm's length. Much closer to the Moon's lower left, look for Regulus.

    If you're up well before sunrise on Saturday or Sunday, here's the scene in the west.

    Sky & Telescope diagram


    Sunday, January 31

  • How many times have you looked at Orion's Belt with binoculars and not noticed "Orion's S"? See the February Sky & Telescope, page 59, for this rather obvious but rarely remarked asterism.

    Monday, February 1

  • By 10 or 11 p.m. the waning Moon is up and shining in the east. Look about a fist-width to its lower left for Saturn.
  • The red long-period variable star R Pegasi, just off the Great Square of Pegasus, should be at maximum light (7th or 8th magnitude) this week. See the chart in the February Sky & Telescope, page 57. This is a project for early evening, before the Great Square sinks low in the west.

    Tuesday, February 2

  • The asteroid 4 Vesta, in Leo, is an easy binocular target all month. It's currently magnitude 6.4, and it will reach magnitude 6.1 at opposition on the night of February 17th. See the finder chart in the February Sky & Telescope, page 54, or online.

    Wednesday, February 3

  • The waning gibbous Moon is up in the east-northeast by midnight tonight. Look for Spica a few degrees upper left of it, and Saturn higher above them.

    Thursday, February 4

  • Mars is passing 3° north of the Beehive Star Cluster.
  • The bright eclipsing variable star Algol should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 12:56 a.m. Friday morning EST; 9:56 p.m. Thursday evening PST. Algol takes several additional hours to fade and to rebrighten. Use our comparison-star chart. For all times of Algol's minima this month, good worldwide, see the February Sky & Telescope, page 59.

    Friday, February 5

  • Last-quarter Moon (exact at 6:48 p.m. EST).

    Saturday, February 6

  • Once Saturn rises into good view late tonight, a small scope will show its largest satellite, Titan, about four ring-lengths to the planet's east.
  • If you're up in early dawn Sunday morning, look for Antares 3° or 4° lower left of the waning crescent Moon (as seen from North America).

    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).

    Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.

    Alan MacRobert

    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 more detailed and descriptive 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? 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 and a curious mind." Without these, "the sky never becomes a friendly place."

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

    This Week's Planet Roundup

    Mercury (magnitude –0.2) remains visible low in the dawn. Look for it just above the east-southeast horizon about 45 minutes before your local sunrise time. Binoculars help. Don't confuse it with Antares far to its upper right, or Altair far to its upper left.

    Venus is hidden behind the glare of the Sun.

    Mars on Feb. 2-3, 2010

    Dramatic things are happening on Mars's north polar cap (bottom) as it shrinks in the Martian springtime. Note the yellow dust storm on the cap's left side here, and the dulling of its right side compared to recent imagery in which it was bright white. At top are dark Mare Erythraeum, Margaritifer Sinus, Aurorae Sinus, and the Solis Lacus region. Lower left of center are dark Niliacus Lacus and Mare Acidalium. Note the many white clouds.

    Veteran planetary imager Donald C. Parker of Coral Gables, Florida, took this superb image on the evening of February 2nd (at 4:00 Feb. 3 Universal Time), when the central meridian longitude was 62°. Click on the image for larger views and more information. South is up.

    Parker used a 16-inch Newtonian reflector and a Skynyx 2-0 camera. Stacked-video imagery like this can show detail on a planet much more clearly than the eye can see through the same telescope.

    Donald C. Parker


    Mars, fiery bright at magnitude –1.3, shines low in the east-northeast in twilight and higher in the east later in the evening. It's in Cancer, more than halfway from Regulus below it to Pollux and Castor above it. Mars is highest in the south by 11 or midnight. Binoculars show M44, the Beehive Star Cluster, about 3° more or less to Mars's south this week.

    In a telescope Mars is still 14.0 arcseconds wide; it passed closest to Earth on January 27th and was at opposition on the 29th. The big, white north polar cap is in fine view, though fading in brilliance due to dust. Identify other surface features using the Mars map and observing guide in the December Sky & Telescope, page 57.

    Jupiter (magnitude –2.0) shines low in the west-southwest in twilight and sets around twilight's end.

    Saturn (magnitude +0.7, in Virgo) rises in the east around 9 or 10 p.m. and stands highest in the south around 3 a.m. In a telescope Saturn's rings are tilted only 4.7° from edge-on to us, and they'll narrow further in the coming months.

    Uranus (magnitude 5.9, just south of the Circlet of Pisces) is getting low in the southwest just after dusk.

    Neptune is lost in the sunset.

    Pluto is very low in the east-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 (also known as UT, UTC, or GMT) minus 5 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.

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