Sky at a Glance | August 6th, 2010

Some daily events in the changing sky for August 6 – 14.

Planets low in the twilight
Venus continues as the bright landmark for shy Mars and Saturn after sunset.

Friday, Aug. 6

  • Starting this evening, Mars and Saturn spend more than a week sliding above brilliant Venus low in the west as twilight fades.

  • Have you seen any early Perseid meteors yet? The peak of the shower is expected to arrive next Thursday night (the night of August 12-13), so start planning now! See our article Dark Nights for the Perseids.

    Saturday, Aug. 7

  • Venus, Mars, and Saturn are gathered their most tightly this evening, fitting in a circle 4.8° in diameter — just small enough to qualify as a "planetary trio" (a grouping within a 5° circle).

    Sunday, August 8

  • Keep watching the Venus-Saturn-Mars triangle as it changes shape day by day in the western twilight. Spica too is now moving in on the scene from the left, as shown above. Can you also make out Gamma (γ) Virginis, magnitude 2.7? For this you'll probably need binoculars.

    Monday, August 9

  • New Moon (exact at 11:08 p.m. Eastern Daylight Time).

    Tuesday, August 10

  • Bright Vega crosses nearest your zenith around 10 or 11 p.m. daylight-saving time (depending on how far east or west you live in your time zone). When you see Vega nearest the zenith, that means the Teapot of Sagittarius is at its highest in the south.

  • The Sagittarius Teapot has no less than eight globular clusters around its spout. Make it a project to ferret them out with your scope, using Sue French's Deep-Sky Wonders column and chart in the August Sky & Telescope, page 64.

    Wednesday, August 11

  • The thin crescent Moon is a few degrees lower left of Mercury, extremely low in the west 15 to 30 minutes after sunset as shown below. This is a lovely but difficult observation, even with binoculars.

  • The Perseid meteor shower will be very active late tonight. See Dark Nights for the Perseids.

    View in bright twilight
    The waxing Moon joins the changing planet scene late in the week. (The visibility of the fainter objects in bright twilight is exaggerated here. These scenes are drawn for the middle of North America; European observers should move each Moon symbol a quarter of the way toward the one for the previous date. In the Far East, move it halfway.)

    Thursday, August 12

  • In twilight, look for the waxing crescent Moon about 7° below the Venus-Saturn-Mars triplet very low in the west.

  • In that planetary triplet, Mars remains within 3° of Venus from now through the 25th.

  • The Perseid meteors should be at their peak late tonight. See Dark Nights for the Perseids.

    Friday, August 13

  • Low in the west in twilight, the crescent Moon is about 10° left of Venus, as shown above.

    Saturday, August 14

  • Arcturus is the brightest star high in the west after dusk (high above the place where Venus declines and sets). At about the same height to its right in the northwest, look for the Big Dipper now turning right-side up. Nearly as high in the northeast, W-shaped Cassiopeia is climbing upward.


    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 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 your 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

    Mercury (about magnitude +0.3) is fading and sinking very low in bright twilight. About a half hour after sunset, use binoculars to look for it just above the horizon due west, well to the lower right of bright Venus.

    Venus (magnitude –4.3) is the bright Evening Star sinking low in the west as twilight fades. In a telescope Venus appears half lit.

    Mars and Saturn (magnitudes 1.5 and 1.1, respectively) are above brilliant Venus in twilight, forming a triangle with it. Look carefully; they're less than 1% as bright. The triangle changes shape daily.

    Jupiter on July 31, 2010
    The side of Jupiter away from the Great Red Spot is still showing only very thin, broken traces of the South Equatorial Belt (SEB). The SEB is normally about as wide and dark as the North Equatorial Belt, seen here below center. The SEB probably still exists but is hidden under a new layer of white, high-altitude ammonia clouds. These clouds could start to clear at any time, allowing a view once again of the belt below.


    S&T's Sean Walker took this image from New Hampshire on the morning of July 31st, at 7:47 UT. The satellite at lower right is sulfury Io.

    S&T: Sean Walker

    Jupiter (magnitude –2.7, in Pisces) rises around the end of twilight and shines high in the southeast by midnight. It's highest in the south during the early-morning hours — the brightest starlike point in the morning sky.

    Jupiter's Great Red Spot is near System II longitude 150°. Assuming it stays there, here's a list to print out of all the Great Red Spot's predicted transit times for the rest of 2010.

    Uranus (magnitude 5.8, in Pisces) is 3° west of Jupiter. In a telescope Uranus is only 3.6 arcseconds wide, compared to Jupiter's 47″.

    Neptune (magnitude 7.8, at the Aquarius-Capricornus border) is up high by late evening. See our finder charts for Uranus and Neptune in 2010.

    Pluto (magnitude 14, in northwestern Sagittarius) is highest in the south right after dark, and there's no moonlight until the end of the week. See our big Pluto finder charts in the July Sky & Telescope, page 60.


    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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