Top 5 Most Recent Articles
  1. The May-June 2013 Planet Dance
  2. The Ring Nebula's Most Detailed Images
  3. Southern Stars at NEAF 2013
  4. This Week's Sky at a Glance
  5. Uranus & Neptune: Thin Weather Layers
Top 5 Most Popular Articles
  1. The Ring Nebula's Most Detailed Images
  2. The May-June 2013 Planet Dance
  3. May 20 - 26, 2013
  4. A Bright Flash in the (Lunar) Night
  5. The Eclipses of May 2013
Top 5 Most Emailed Articles
  1. The May-June 2013 Planet Dance
  2. This Week's Sky at a Glance
  3. Watch Three Planets Dancing in Twilight
  4. Digitizing Harvard’s Century of Sky
  5. A Cosmic Sleight of Hand


home > observing > this week's sky at a glance
email this > print this > save this > rss >
SkyWeek Television Show
Click here to watch this week's episode Click here to watch this week's episode

Watch SkyWeek

As seen on PBS television stations nationwide

Sponsors:

Meade Instruments
Woodland Hills Camera & Telescope

This Week's Sky at a Glance

Some daily events in the changing sky for October 21 – 29

by Alan M. MacRobert

Friday, Oct. 21

  • The modest Orionid meteor shower should peak in the early morning hours of Saturday. You might count a dozen or more Orionids per hour under ideal observing conditions. Some are also visible for several mornings before and after.

  • The Moon, just past last quarter, shines near Regulus below Mars before and during dawn Saturday morning, as shown below.

    Dawn view
    On Saturday morning the 22nd, Mars shines above the Moon and Regulus.
    Sky & Telescope diagram
    .

    Saturday, Oct. 22

  • Fomalhaut, the Autumn Star, shines low in the south-southeast after dusk. It's due south later in the evening. The western (right-hand) edge of the Great Square of Pegasus, very high in the sky, points down nearly to it.

    Sunday, Oct. 23

  • The summery constellation Cygnus remains nearly overhead after dinnertime, even higher than bright Vega when you face west and crane your neck. Have you hunted out the subtle star clusters in Cygnus's Milky-Way-rich center? See Sue French's "Deep-Sky Wonders" article, finder chart, and photos in the October Sky & Telescope, page 56.

    Monday, Oct. 24

  • The tiny black shadow of Jupiter's satellite Europa crosses Jupiter tonight from 12:26 to 2:54 a.m. Tuesday morning Eastern Daylight Time (9:26 to 11:54 p.m. Monday evening Pacific Daylight Time). Europa itself follows only about 15 minutes behind its shadow.

    Tuesday, Oct. 25

  • By 9 or 10 p.m. the Autumn Star, Fomalhaut, shines at its highest in the south (not all that high). Fomalhaut is 25 light-years away — exactly the same distance as Vega, shining brighter high in the west. So, the difference in brightness that you see is the two stars' actual difference in true luminosity. Vega looks 1 magnitude brighter than Fomalhaut (in other words, 2.5 times brighter), and so it really is.

    Wednesday, Oct. 26

  • The Ghost of Summer Suns. Halloween is approaching, and this means that Arcturus, the star sparkling low in the west-northwest in twilight, is taking on its role as "the Ghost of Summer Suns." What does this mean? For several days centered on October 29th every year, Arcturus occupies a special place in the sky above your local landscape. It closely marks the spot there where the Sun stood at exactly the same time (by your clock) during warm June and July — in broad daylight, of course! So, in the last days of October each year, you can think of Arcturus as the chilly Halloween ghost of the departed summer Sun.

  • New Moon (exact at 3:56 p.m. EDT).

    Thursday, Oct. 27

  • The shadow of Jupiter's moon Io starts crossing Jupiter around 11:19 p.m. EDT, followed by Io itself just 3 minutes behind almost on top of the shadow.

    Then at 11:37 p.m. EDT, Ganymede disappears into eclipse by Jupiter's own shadow, just a hairsbreadth beyond Jupiter's western limb.

    The arrangement in bright twilight
    The waxing crescent Moon points the way to low Venus and even lower Mercury. (The visibility of the fainter objects in bright twilight is exaggerated. 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.)
    Sky & Telescope diagram
    Friday, Oct. 28

  • In bright twilight, look for the thin waxing crescent Moon very low in the southwest. Can you spot Venus to its lower right, as shown here? They're separated by roughly a fist-width at arm's length (depending on your longitude). Use binoculars to try for much fainter Antares and Mercury.

  • Jupiter is at opposition tonight, opposite the Sun as seen from Earth. Like last year's opposition, this is an unusually close one; see Jupiter under "This Week's Planet Roundup" below.

    Saturday, Oct. 29

  • The crescent Moon is higher and easier to spot now after sunset than it was yesterday. The moon's round limb points to the lower right, toward very low Venus and Mercury as shown here.




    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).

    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 81,312 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 — to hunt among the stars.
    Sky & Telescope
    Once you get a telescope, to put it to good use you     must have a detailed, large-scale sky atlas (set of charts). The standards are the 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 new 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 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."




    This Week's Planet Roundup

    Mercury (about magnitude –0.3) is deep in the sunset below much-brighter Venus. If the air is very clear, use binoculars or a telescope about 15 or 20 minutes after sundown this week to see if you can pick up Mercury 3° lower right of Venus early in the week, and 2° below Venus later in the week.

    Venus (magnitude –3.8) is a little above the west-southwest horizon 20 or 30 minutes after sunset. It's getting less difficult to spot every week.

    Mars (magnitude +1.2, in Leo) rises around 1 or 2 a.m. daylight-saving time. By the beginning of dawn it's in good view high in the east-southeast. Mars is closing in on similarly bright Regulus below it. They're 10° apart on October 22nd and 7° apart on the 29th. In a telescope Mars is a tiny blob only 5.7 arcseconds wide.

    Jupiter on Sept. 19, 2011
    Io and darker Callisto were just east of Jupiter when S&T's Sean Walker imaged the scene on the morning of September 19th. South is up. Note the reddish Oval BA, "Red Spot Junior," just past the central meridian in the South Temperate Belt.
    S&T: Sean Walker
    . Jupiter (magnitude –2.9, in southern Aries) shines low in the east-northeast in twilight, then blazes higher in the east to southeast all evening. Look above it for the stars of Aries and below it for the head of Cetus, rather dim. Jupiter is nearly at its highest in the south by midnight. It's a big 49 arcseconds wide, as big as it will appear at its October 28th opposition.

    Moreover, this is an unusually close Jupiter opposition. Last year Jupiter came closer to Earth than it had since 1963. This year it's only an insignificant 0.4% farther. See our guide to observing Jupiter with a telescope.

    Saturn is deep in the glow of sunrise.

    Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are well placed in the south and southeast by mid-evening. Use our printable finder chart for both, or see the September Sky & Telescope, page 53.

    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.

    NEW BOOK: Sue French's DEEP-SKY WONDERS! This big, long-awaited observing guide by Sky & Telescope's Sue French is now available from Shop at Sky. Hefty and lavishly illustrated, it contains Sue’s 100 favorite sky tours (25 per season), with finder charts, from her 11 years of writing the Celestial Sampler and Deep-Sky Wonders columns for S&T. Don’t miss it!

    To be sure to get the current Sky at a Glance, bookmark this URL:
    http://SkyandTelescope.com/observing/ataglance?1=1

    If pictures fail to load, refresh the page. If they still fail to load, change the 1 at the end of the URL to any other character and try again.

    • Sky at a Glance Archive


    Sky Publishing, a New Track Media Company
    Copyright © 2013 New Track Media. All rights reserved.
    Sky & Telescope, Night Sky, and SkyandTelescope.com are registered trademarks of New Track Media