Sky at a Glance | August 19th, 2011

Midnight scene
Late at night, the waning Moon passes bright Jupiter.

Friday, August 19

  • Watch bright Jupiter rise below the waning gibbous Moon late tonight. They'll be up in the east by about 11 or midnight daylight saving time, as shown here, depending on where you live in your time zone. They're best seen in a telescope when very high before dawn tomorrow morning.

    Saturday, August 20

  • Vesta, the brightest asteroid — and host to NASA's Dawn spacecraft — is well up in fine view by mid- to late evening, shining in Capricornus at magnitude 6.0. It's an easy find in binoculars. Use the chart in the August Sky & Telescope, page 53, or our Vesta and Ceres finder charts online.

    Ceres, a future destination for Dawn, lurks two constellations farther east in Cetus. It's currently magnitude 8.0.

    Sunday, August 21

  • Last-quarter Moon (exact at 5:54 p.m. EDT). Once the Moon rises around midnight, look above it for the Pleiades, as shown above.

    Monday, August 22

  • Neptune, in Capricornus, is at opposition tonight.

    Tuesday, August 23

  • Here it is still only August, with summer only 2/3 of the way through — but already the Great Square of Pegasus is up in the east after dark, balancing low on one corner.

    Dawn view
    The waning crescent Moon passes Mars in Gemini at dawn. (Although Mercury is plotted here, it's too faint in the bright morning twilight to see without optical aid.)

    Wednesday, August 24

  • As dawn begins to brighten on Thursday morning the 25th, look for Mars to the left of the thin crescent Moon (for North America), as shown here.

    Thursday, August 25

  • Did you know that two tiny planetary nebulae lurk right near the big, familiar Wild Duck star cluster, M11 in Scutum? One of them can be spotted in many amateur telescopes, especially with an O III filter. The other is a stiffer challenge. See Sue French's Deep-Sky Wonders column, chart, and photo in the August Sky & Telescope, page 58.

    Friday, August 26

  • Jupiter's Great Red Spot (currently pale orange) should be crossing the planet's central meridian around 3:09 a.m. Saturday morning EDT. For all Red Spot transits in August, as well as all Jupiter satellite events, see "Action at Jupiter" in the August Sky & Telescope, page 54.

    Saturday, August 27

  • The two brightest stars of summer are icy white Vega, now high overhead at dusk (if you live in the mid-northern latitudes), and Arcturus, pale yellow-orange, shining lower in the west.

  • The shadow of Ganymede, Jupiter's biggest moon, crosses Jupiter's face from 1:36 to 3:41 a.m. Sunday morning Eastern Daylight Time.


    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 Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper 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 Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive 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

    Mars on Aug. 13, 2011
    If you have any doubt that stacked-video imaging can do black magic on the planets compared to what you see by eye in the same telescope, look at this. Mars was a mere 4.5 arcseconds wide on August 13th when John Boudreau of Saugus, Massachusetts, took this image with an 11-inch scope. Visually, Mars at that size is a tiny, featureless fuzzblob. Go look if you don't believe me.


    Click for animation of two images showing 7 minutes of the planet's rotation. This makes it easy to see what features here are real rather than noise. Hint: Most of them are.


    Boudreau used a C-11 telescope at f/38 with a PGR Flea 3 camera and Astrodon RGB color filters. He rated the seeing only 6 or 7 on a scale of 10. And the planet was only 32° high. (South is up.)

    John Boudreau

    Mercury and Venus are hidden deep in the glow of the Sun.

    Mars (magnitude +1.4, crossing Gemini) rises around 2 a.m. daylight-saving time. By the beginning of dawn it's in good view up in the east. In a telescope, Mars is just a very tiny blob only 4.6 arcseconds in diameter.

    Jupiter (magnitude –2.6, in southern Aries) rises in the east-northeast around 11 p.m. daylight saving time. Look above it for the little star pattern of Aries and (once Jupiter is well up) closer below it for the head of Cetus, rather dim. By early dawn Jupiter shines very high in the south, making this the best time to examine it with a telescope. It appears 40 arcseconds wide.

    Saturn (magnitude +0.9, in Virgo) is sinking ever lower in the west-southwest at dusk. Look for it far below high, bright Arcturus. Left of Saturn by 11° twinkles Spica.

    Uranus (magnitude 5.8, near the Circlet of Pisces) and Neptune (magnitude 7.8, in western Aquarius) are well up in the southeastern part of the sky before midnight. Here's our printable finder chart for both.

    Jupiter on Aug. 16, 2011
    Equatorial Zone looks very complex. The [broad, dark] South Equatorial Belt [above center] is very complex. Note the tiny white ovals lining up on the southern edge of the SEB." Go now uses a C-14 scope." credits="Christopher Go" width="" height="" align="right"]
    Pluto (magnitude 14.0, in northern Sagittarius) is highest in the south right after dark; don't delay. A big finder chart for it is in the July Sky & Telescope, page 64.


    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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