Sky at a Glance | August 28th, 2009

Some daily events in the changing sky for August 28 – September 5.

Friday, August 28

  • Before dawn begins Saturday morning, spot Mars high in the east (in the feet of Gemini). Use binoculars to find the open star cluster M35 lurking just 1° to Mars's left. For a parallel planet-and-cluster event before dawn later this week, see September 1 below.

    Saturday, August 29

  • The Moon this evening shines near the top of the Sagittarius Teapot: the 3rd-magnitude star Lambda Sagittarii.

    Sunday, August 30

  • After dark this evening the gibbous Moon shines in the south, and Jupiter shines in the southeast. High above them, forming a nearly equilateral triangle with them, is Altair, the eye of Aquila, the Eagle. Vega poses near the zenith.

  • Jupiter's Great Red Spot should cross Jupiter's central meridian (the imaginary line down the center of the planet's disk from pole to pole) around 12:15 a.m. Monday morning EDT (9:15 p.m. Sunday evening PDT). The "red" spot appears pale orange-tan, as seen below. It should be visible for about an hour before and after in a good 4-inch telescope if the atmospheric seeing is sharp and steady. A light blue or green filter helps. The Red Spot transits about every 9 hours 56 minutes.
    Jupiter on the evening of Sept. 2, 2009
    This year, Jupiter's Great Red Spot has been nicely bordered by the thick white line of the Red Spot Hollow,which indents the dark South Equatorial Belt. Note the very dark red barge following behind the pale Red Spot. The North Equatorial Belt is full of turbulence, including a big blue plume. Far to the right (celestial east), Ganymede and Europa are in conjunction. S&T's Sean Walker took this image at 1:15 UT September 3, 2009. South is up.


    For all of the Red Spot's central-meridian crossing times, good worldwide, use our Red Spot calculator, or print out our list for the rest of 2009.

    S&T: Sean Walker

    Monday, August 31

  • With summer now winding down, as soon as darkness falls you'll find that Cassiopeia has risen as high in the northeast as the Big Dipper has declined in the northwest.

  • Jupiter's Red Spot should transit around 8:06 p.m. EDT.

    Although the Moon and Jupiter look close together on Tuesday and Wednesday evenings, Jupiter is actually 1,500 times farther away — and 40 times larger in diameter. Faint, 8th-magnitude Neptune is 7 times farther than Jupiter. (This scene is 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.)
    Tuesday, Sept. 1

  • Jupiter shines left of the Moon this evening, as shown here.

  • Before dawn this morning and Wednesday morning, binoculars show the Beehive star cluster (M44) just 1° left or upper left of dazzling Venus.

    Wednesday, Sept. 2

  • Jupiter is the "star" to the lower right of the Moon tonight, as shown at right.

  • Jupiter's Red Spot should transit around 9:45 p.m. EDT.

  • Jupiter displays no visible moons in a small telescope from 12:43 to 2:29 a.m. Thursday morning EDT (9:43 to 11:29 p.m. Wednesday evening PDT). All four are either in front of the planet, behind it, or in its shadow. This won't happen again until 2019, according to astro-calculator Jean Meeus.

    Shortly afterward there's a double shadow transit on Jupiter, from 11:42 p.m. 12:47 a.m. PDT. And there's more going on too; details.

    For a timetable of all of Jupiter's satellite phenomena throughout September, good worldwide, see the September Sky & Telescope, page 56.

    Thursday, Sept. 3

  • The recurrent nova U Scorpii still hasn't blown up, as at least one astronomer expects it should this year, and its position in northernmost Scorpius is starting to descend for the season. Keep watch using the article in the August Sky & Telescope, page 56, or the charts here.

    Friday, Sept. 4

  • Full Moon (exact at 12:03 p.m. EDT).

  • Jupiter's Red Spot should transit around 11:23 p.m. EDT.

  • Saturn's rings are turned edge-on the Earth today for the first time since 1996. Unfortunately, Saturn is buried too deep in the sunset for telescopic observing.

    Saturday, Sept. 5

  • This is the time of year when, during evening, the bowl of the Little Dipper (mostly faint) pours into the bowl of the Big Dipper. Look north-northwest. In springtime the situation is reversed, and they're in the north-northeast.


    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 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'll need a detailed, large-scale sky atlas (set of charts; the standards are
    Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.

    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 and a curious mind." Without these, "the sky never becomes a friendly place."

    More beginners' tips: "How to Start Right in Astronomy".


    This Week's Planet Roundup

    Mars on Sept. 2, 2009
    It's starting to be Mars season again — barely. The planet is high in the morning sky but only 6 arcseconds wide. Nevertheless, S&T's Sean Walker managed to record some surface detail on the morning of September 2nd. The dark area at top includes Mare Sirenum and Mare Cimmerium. The small spot just upper left of center is Phoenicis Lacus. Note the north polar haze. South is up. Walker used a 12.5-inch reflector and IRGB color filters for this stacked-video image.
    S&T: Sean Walker
    Mercury and Saturn are disappearing deep into the sunset. If you're ambitious, try sweeping for them with binoculars (preferably tripod-mounted) just above the horizon due west about 20 minutes after sunset. Saturn is getting farther to Mercury's right day by day. Don't be misled by Spica, sparkling off to their upper left.

    Venus (magnitude –4.0, in Cancer) blazes in the east before and during dawn. Look for Procyon off to its right, and Sirius much farther to Procyon's right (and probably somewhat lower, depending on where you live).

    Mars (magnitude +1.0, in the feet of Gemini) is high to the upper right of Venus before dawn. In a telescope it's still only 6 arcseconds wide: a tiny, fuzzy blob. Mars is on its way to a mediocre opposition late next January, when it will appear no larger than 14 arcseconds wide.

    Jupiter (magnitude –2.8, in Capricornus) comes into view in the southeast as twilight fades — the first "star" to appear after sunset. It's higher in better telescopic view by 10 p.m.

    Polar projection animation
    Watch the impact mark spread and grow over the course of four weeks! It's the dark mark near the pole at the 2 o'clock position. Theo Ramakers writes, "Here is an updated animation containing the images of a large number of dedicated Jupiter imagers, members of the ALPO Jupiter listserve. Hans Joerg Mettig from Jupos.com in Germany converted the submitted images to a polar projection, and I put them together in an animation."


    Notice the rather that just spreading out, the original impact site seems to keep pouring out black stuff that then drifts away.

    Theo Ramakers
    Jupiter impact mark fades. A black dust marking, like those made by the Comet Shoemaker-Levy 9 impacts in 1994, appeared suddenly in Jupiter's south polar region on July 19th. Backyard observers tracked it as it spread and elongated. Now it has broken up and faded nearly to invisibility. See our article.

    Uranus (magnitude 5.8, just below the Circlet of Pisces) is well up in the southeast by 10 p.m.

    Neptune (magnitude 7.8, in Capricornus) appears 5° from Jupiter but 20,000 times fainter. See our finder charts for Uranus and Neptune.

    Pluto (14th magnitude, in northwestern Sagittarius) is still well up in the south-southwest right after dark. See the finder chart in the June Sky & Telescope, page 53.

    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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