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This Week's Sky at a Glance

by Alan M. MacRobert

Some daily events in the changing sky for October 9 – 17.

The Moon joins the dawn planet scene on the mornings of the 15th and 16th. (The visibility of faint objects in bright twilight is exaggerated here.)
Sky & Telescope diagram
Friday, October 9

  • There's a growing chill to the October evenings, at least in New England where I live, and by midevening the eastern sky holds harbingers of the winter constellations to come. By 9 or 10 p.m. Capella and the stars of Auriga sparkle in the northeast. To their right, at about the same height in the east-northeast, the Pleiades are coming into view. See the scene below.

    Saturday, October 10

  • Jupiter's Great Red Spot should transit the planet's central meridian around 11:13 p.m. EDT. (For all of the Red Spot's transit times, good worldwide, use our Red Spot calculator or print out our list for the rest of 2009.)

  • The last-quarter Moon rises late tonight. It's exactly last quarter at 4:56 a.m. Sunday morning EDT.

    Sunday, October 11

  • Early Monday morning the Moon, Mars, Pollux, and Castor form a squiggly line about 20° long, in that order from bottom to top.

    Monday, October 12

  • Jupiter ends its retrograde (westward) motion against the background stars, and gradually starts creeping east again. But it happens slowly enough that Jupiter appears to be practically stationary among the stars all this week. For the rest of October, watch Jupiter move slowly toward the faint, magnitude-4.3 star Iota Capricorni just to its east. (Binoculars help.)

  • Jupiter's Red Spot should transit around 12:51 a.m. Tuesday morning EDT; 9:51 p.m. Monday evening PDT.

  • During the early morning hours of Tuesday, Mars lies in a straight line with Pollux and Castor above it.

    Tuesday, October 13

  • Jupiter's Red Spot should transit around 8:43 p.m. EDT.

    Wednesday, October 14

  • Jupiter's moon Callisto casts its tiny black shadow onto Jupiter tonight from 8:23 p.m. to 1:00 a.m. EDT. (For a list of all such events among Jupiter's moons this month, visible worldwide, see the October Sky & Telescope, page 58.)

    Thursday, October 15

  • Jupiter's Red Spot should transit around 10:21 p.m. EDT.

  • From now through the end of the month, the zodiacal light ("false dawn") is in good view in the moonless eastern sky before the first sign of actual dawn — if you have a very clear sky and no significant light pollution. Look for a huge, narrow pyramid of light extending up from the eastern horizon at an angle along the constellations of the zodiac.

  • Once dawn is well under way Friday morning, look for the thin waning crescent Moon about 6° to the right of Venus low in the east (for North America). Faint Saturn is about 3.3° above Venus, and Mercury is 8° to Venus's lower left, as shown above. Bring binoculars.

    Friday, October 16

  • The Great World Wide Star Count continues through this week. Go outside, follow the directions to estimate how dark your sky is, and enter it into a worldwide database — it's fun!

  • During the evening this month, look very high to Jupiter's upper right for bright Altair. Look from Jupiter in exactly the opposite direction for Fomalhaut on the rise. Both are near stellar neighbors, as stars go; Altair is 17 light-years away, and Fomalhaut is 25. Jupiter, by comparison, is currently 37 light-minutes from Earth.

    Saturday, October 17

  • New Moon (exact at 1:33 a.m. Sunday morning EDT).

  • Jupiter's Red Spot should transit at midnight tonight EDT; 9:00 p.m. PDT.

    Eastward late-evening view
    The Pleiades and Aldebaran shine in the east these evenings, and Capella sparkles in the east-northeast. To Capella's right are the three moderately dim stars called "the Kids" (as in baby goats; Capella is the Goat Star). One of them, Epsilon Aurigae, has begun to fade into its much-awaited, two-year-long partial eclipse. See our article with a comparison-star chart, and our big feature on this mysterious star in the May Sky & Telescope, page 58.
    Sky & Telescope diagram
    .



    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, Deluxe Edition
    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.
    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 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

    Venus, Mercury, and Saturn are low in the east during dawn, changing configuration daily. Venus is by far the brightest. Mercury is sinking lower to the horizon below it. Saturn just had a close conjunction with Mercury on October 8th and a close conjunction with Venus on October 13th.

    Mercury is magnitude –0.9 but becoming more dimmed by atmospheric extinction. Saturn is a forlorn magnitude +1.1. Venus shines 100 times brighter than Saturn at magnitude –3.9. Bring binoculars! And see our article about this dawn planet dance.

    Best viewing may be about 50 minutes before your local sunrise time. And when exactly is that? You can always find your sunrise and sunset times (and much else) once you put your location into our online almanac. (If you're on daylight saving time like most of North America, make sure the Daylight Saving Time box is checked.)

    Stay up after midnight to make the acquaintance of Mars. For a few days, the Moon helps point the way. (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 drawn three times actual size.)
    Sky & Telescope diagram
    Mars (magnitude +0.7) rises around midnight and is very high in the southeast before dawn. It's near Gemini's head stars, Pollux and Castor. In a telescope Mars is still only 7 arcseconds wide: a tiny, fuzzy blob, though noticeably gibbous. Mars is on its way to an unremarkable opposition late next January, when it will be 14 arcseconds wide.

    Jupiter (magnitude –2.6, in Capricornus) shines brightly in the south-southeast as twilight fades — it's the first "star" to appear after sunset. Jupiter is in quadrature (90° east of the Sun) on October 6th, so all month it displays its greatest difference in lighting between its east and west sides: not dramatic in a telescope, but noticeable.

    Uranus (magnitude 5.7, below the Circlet of Pisces) is well up in the southeast during evening.

    Neptune (magnitude 7.8) is in Capricornus 7° east of Jupiter.

    See our finder charts for Uranus and Neptune. For a guide to spotting the challenging satellites of Uranus and Neptune at any date and time (you'll need a fairly big scope), see the October Sky & Telescope, page 59. October 10th marks the 163rd anniversary of William Lassell's discovery of Neptune's big moon Triton.

    Pluto (14th magnitude, in Sagittarius) is sinking low in the southwest after dark.

    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 Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.

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