Sky at a Glance | October 18th, 2013

Penumbral eclipse
The Moon at the middle of its penumbral eclipse on November 28, 2012, and afterward, photographed from the Philippines. The October 18th penumbral eclipse will be almost as deep around 7:50 p.m. EDT.

Friday, October 18

  • Full Moon. A slight penumbral eclipse of the Moon will be detectable this evening by careful Moon-watchers in the eastern half of North America. The Moon will pass deepest through the pale outer fringe (penumbra) of Earth's shadow around 7:50 p.m. Eastern Daylight Time (EDT). Look for unusual shading on the Moon's south-southeastern side. Weaker shading should be detectable for at least 45 minutes before and after.

    In Europe and Africa, the penumbral eclipse happens in the middle of the night when the Moon is high: centered on 23:50 Universal Time (GMT). Details and world map.

  • More cosmic shadow action! A double shadow transit takes place on Jupiter tonight from 6:25 to 8:37 UT October 19th (2:25 to 4:37 a.m. Eastern Daylight Time Saturday morning). Both Io and Europa will be casting their tiny black shadows onto the planet's face at once. Both shadows leave Jupiter's western edge almost simultaneously — just as Europa itself is beginning to cross in front of Jupiter's eastern edge.

    During this, Jupiter's Great Red Spot is in view. It should cross the planet's central meridian around 3:25 a.m. EDT Sunday morning.

    Dusk view
    Having passed Venus, Antares is finally blinking its low farewell for the year. Watch it pull farther from Venus day by day.

    Saturday, October 19

  • Look about a fist-width above the Moon this evening for the main stars of little Aries, lined up nearly horizontally.

    Sunday, October 20

  • This week, face southwest soon after dark and look high for Altair. It's the bright eye of Aquila, the Eagle, most of which now hangs down below it. Look to Altair's upper left, by about a fist and a half at arm's length, for little Delphinus, the Dolphin, leaping upward.

    Look almost as far to Altair's upper right for Sagitta, the Arrow, even fainter and smaller.

    Monday, October 21

  • Lonely Fomalhaut, the Autumn Star, is at its highest in the south around 9 or 10 p.m. this week.

    Tuesday, October 22

  • It's October — so have you tried to spot the companion of Sirius yet? Accompanying Sirius is the first-discovered white dwarf, 1/10,000 as bright and currently 10.0 arcseconds to its east. Early dawn in October is an excellent time to look for it, for reasons that Alan Whitman explains in the October Sky & Telescope, page 30.

    Last Tuesday morning, Whitman spotted Sirius B surprisingly easily in a big scope: it "was seen immediately in my 16-inch at 261x (7mm orthoscopic eyepiece) with a lunar filter (since I hadn't thought to bring out my occulting-bar eyepiece)." It's possible in much smaller scopes too — given first-rate dawn seeing.

    Wednesday, October 23

  • Below the feet of Aquarius, off the eastern end of Capricornus, are the Helix Nebula and a crowd of lesser-known galaxies. Now that the Moon is gone from the after-dinner sky, explore them with your telescope using Sue French's Deep-Sky Wonders column, chart, and photos in the October Sky & Telescope, page 56.

    Thursday, October 24

  • The Moon rises around 10 or 11 tonight (depending on where you are), with bright Jupiter to its left or lower left. Farther left is Pollux, with Castor above it. By the beginning of dawn Friday morning, they're all high in the south (above Procyon).

    Friday, October 25

  • Staying out late tonight? Keep an eye to the low east-northeast for Jupiter rising around 11 or midnight (depending on your location). Castor and Pollux shine to its left. About 45 minutes later, the waning gibbous Moon follows it up. And then once the Moon is well up, look to the Moon's lower right for Procyon.

    Saturday, October 26

  • Last-quarter Moon (exactly so at 7:40 p.m. EDT). The Moon rises around midnight or 1 a.m. local time tonight, in dim Cancer below Jupiter and Gemini. To the right of the Moon and Jupiter, Procyon forms a nearly equilateral triangle with them.

    By dawn on Sunday they're all high in the southeast to south, with Procyon now on the bottom and Regulus and Mars off to their lower left.


    Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

    This is an outdoor nature hobby. 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 guide to 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'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

    You'll also want a good deep-sky guidebook, such as Sue French's 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 beloved if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means heavy and expensive). As Terence Dickinson and Alan Dyer say in their invaluable 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

    Jupiter on Sept. 9, 2013
    Oval BA. It shows up on all of my videos this morning."" credits="S&T: Sean Walker" width="" height="" align="right"]
    Mercury and Saturn are buried deep in the glow of sunset, sinking away.

    Venus (magnitude –4.4) shines brightly in the southwest during dusk, gradually moving higher week by week. Can you still see Antares moving farther to its lower right?

    In a telescope Venus appears very close to half-lit. When will (or did) it appear exactly so? Visually, the dichotomy of Venus is seen about a week or ten days before Venus wanes to become geometrically half-lit (which happens on October 30th). We see this offset timing because of the dim lighting at Venus's terminator combined with fuzzy seeing in a telescope and/or a bright sky background.

    Mars (magnitude 1.5) rises around 2 or 3 a.m. near Regulus (magnitude 1.4) in Leo. By dawn they're high in the east. Mars and Regulus are moving farther apart now, from a separation of 2.5° on October 19th to 6.5° on the 26th. In a telescope Mars is just a tiny blob 4.7 arcseconds wide.

    Comet ISON is also near Mars, but it's still a faint telescopic target at about 10th magnitude. Use the finder chart for it in the November Sky & Telescope, page 50.

    Jupiter (magnitude –2.2, in Gemini) rises in the east-northeast around 11 p.m. and blazes high in the south by early dawn. About 8° left of it after it rises are Castor and Pollux.

    Uranus on Oct 6, 2013
    Unlike the blank face that Uranus showed during Voyager 2's 1986 flyby, Uranus is now displaying belts and lighter zones — to the unusually capable imagers who can capture them! Damian Peach in England took this shot on October 6th when Uranus was just 3.7 arcseconds wide. He used a 12-inch Schmidt-Cassegrain scope, a deep-red RG610 filter, 35 minutes of video shot at a very slow 3 frames per second due to Uranus's dimess, and software for de-rotating the planet, frame selection, and frame stacking.

    Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.8, in Aquarius) are high in the southeast and south, respectively, by 9 p.m.
    Finder charts for Uranus and Neptune. See also the October Sky & Telescope, page 50.


    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.


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