Sky at a Glance | August 27th, 2010

Planet lineup. Bring binoculars
The changes continue among Venus and company low after sunset. Use binoculars; the visibility of the faint objects in bright twilight is exaggerated here.

Friday, August 27

  • Jupiter shines to the right of the waning gibbous Moon once they rise after dark.

    Saturday, August 28

  • The Venus-Spica-Mars triangle low in the west-southwest in twilight is distorting, as Spica moves closer to Venus.

    Sunday, August 29

  • Jupiter's Great Red Spot should transit the planet's central meridian within a few minutes of 2:25 a.m. Monday morning EDT; 11:25 p.m. Sunday evening PDT.

    Monday, August 30

  • If you're up before dawn Tuesday morning, look for the Pleiades some 6° or 7° left of the waning Moon (for North America), as shown below.

    Tuesday, August 31

  • Use binoculars to look for 1st-magnitude Spica just above Venus low in the fading sunset.

    Wednesday, September 1

  • Bright Venus and faint Spica and Mars form an almost straight line a little less than 5° long, low in the west-southwest about a half hour after sunset as shown here. Note: Despite how the illustration appears, Venus is 175 times brighter than Spica!

    Early risers will catch the last-quarter Moon passing through Taurus high above early Orion.
  • Last-quarter Moon (exact at 1:22 p.m. EDT).

    Thursday, September 2

  • By the beginning of September the Great Square of Pegasus is looming well up in the east after dark, balanced on one corner: the sign of autumn to come. This year bright Jupiter is the landmark; the Great Square is upper left of it in early evening, as shown above.

    Friday, September 3

  • Mira, the prototype red long-period variable star in Cetus, is in its way to a maximum predicted for early October. It's probably not visible to the unaided eye yet but should be easy in binoculars. You'll need to look for it after midnight, however. See the chart in the September Sky & Telescope, page 58.

    Saturday, September 4

  • Low in the west-southwest after sunset, Mars is now just 2° upper right of Spica, which is roughly 4° right of landmark Venus. Cloudy? Try again tomorrow.


    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 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

    Jupiter with two red spots, Aug. 30, 2010
    This is an amateur image? Taken from Earth? Star planetary imager Anthony Wesley in Australia took this stacked-video image on August 30th at 17:38 UT, using the 14.5-inch Newtonian reflector he's pictured with below.


    Jupter's Oval BA, also known as Red Spot Junior, has just passed the Great Red Spot without any visible effect on either. Here, Junior is just south of the Great Red Spot.


    Mercury is hidden in the glare of the Sun.

    Venus, though bright at magnitude –4.4, is quite low in the west-southwest during twilight. It sets by dark.

    Mars, vastly dimmer at magnitude +1.5, is to Venus's right or upper right, as shown here. Look also for similar Spica passing by Venus this week, from upper left to right. They appear closest together on the 31st. Saturn has moved far off to Venus's lower right and may be getting lost by now. Bring binoculars for all three of these faint objects.

    Jupiter (magnitude –2.9, in Pisces) rises in twilight and is well up in the east-southeast by late evening — the brightest starlike point in the sky. It's highest in the south around 2 a.m. daylight saving time.

    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.

    Anthony Wesley and discovery telescope
    Anthony Wesley with his 14.5-inch reflector, seven hours after his historic pre-dawn discovery of the impact flare on Jupiter on June 3, 2010.
    Anthony Weslay

    Uranus (magnitude 5.8, in Pisces) is not quite 2° west of Jupiter. In a telescope Uranus is only 3.7 arcseconds wide, compared to Jupiter's unusually wide 49″.

    Neptune (magnitude 7.8, at the Aquarius-Capricornus border) is up high by mid-evening. See our finder charts for Uranus and Neptune in 2010, also in the September Sky & Telescope, page 56. What colors do Uranus and Neptune seem to show, if any?

    Pluto (magnitude 14, in northwestern Sagittarius) is highest in the south right at the end of dusk, when there's no Moon. See our 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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