Some daily events in the changing sky for September 5 – September 13.

Friday, September 5

  • Jupiter's Great Red Spot (see photo near the bottom of this page) should cross Jupiter's central meridian around 9:38 p.m. Eastern Daylight Time. The "red" spot appears very pale orange-tan. It should be visible for at least 50 minutes before and after in a good 4-inch telescope if the atmospheric seeing is sharp and steady, which it's usually not. A light blue or green filter helps.

    The Red Spot transits about every 10 hours 56 minutes. For all its transit times, good worldwide, see our listing or applet online.

    Watch the bright waxing Moon cross Scorpius and Sagittarius after dark in early September. (These scenes are 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. For clarity, the Moon is shown three times actual size.)

    Alan MacRobert

    Saturday, Sept. 6

  • Look just above the Moon in twilight for Antares sparkling orange-red, as shown at right. Binoculars help.
  • Venus, faint Mercury, and fainter Mars fit in a 3.8° circle from this evening through September 13th. They remain within 5° of each other through the 19th. See the views below, and our article and sky map movie (Quicktime, 1 MB).
  • The bright eclipsing variable star Algol should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:15 p.m. EDT. Algol takes several additional hours to fade and to rebrighten. (For all times of Algol's minima this month, good worldwide, see the September Sky & Telescope, page 64.)

    Sunday, September 7

  • First-quarter moon (exact at 10:04 a.m. EDT).
  • Double shadow transit on Jupiter. Io and bigger Ganymede both cast their tiny black shadows onto Jupiter from 8:12 to 8:38 p.m. EDT (during twilight near the East Coast, daylight to the west).
  • Jupiter's Red Spot transits around 11:17 p.m. EDT.

    Monday, September 8

  • Jupiter is the bright "star" upper left of the Moon this evening.

    Tuesday, September 9

  • Jupiter shines upper right of the Moon. Although they look close together, Jupiter is 1,750 times farther away — and 40 times larger!

    Wednesday, September 10

  • Jupiter's Red Spot transits around 8:47 p.m. EDT.
  • Watch Jupiter's moon Europa slowly reappear from eclipse out of Jupiter's shadow around 11:20 p.m. EDT. It'll be barely east of the planet. (For a listing of all events among Jupiter's moons this month, visible worldwide, see the September Sky & Telescope, page 58.)

    Use binoculars in bright twilight.

    Venus and faint Mars are in conjunction, with Mercury looking on from below.

    Sky & Telescope diagram

    Thursday, September 11

  • Venus is passing about 1/3° north (upper right) of tiny Mars after sunset (viewed from the longitudes of North America), as shown at right. They'll both easily fit in a 50x telescopic field of view.
  • Excellent asteroid occultation. Late tonight, just off the head of Cetus, a 6th-magnitude star should get briefly blacked out by the 10th-magnitude asteroid 9 Metis. The predicted occultation path sweeps from Southern California (including Los Angeles) across Colorado, Iowa, Wisconsin, and Ontario. See the article and maps in the September Sky & Telescope, page 65.

    Friday, September 12

  • Uranus is at opposition: opposite the Sun in our sky.
  • Jupiter's Red Spot transits around 10:26 p.m. EDT.

    Saturday, September 13

  • With summer nearing its end (on September 22nd this year), the Summer Triangle is only now reaching its highest overhead after dark. As the stars come out, look for bright Vega nearly straight up (if you live in the mid-northern latitudes). To Vega's east, by two or three fist-widths at arm's length, look for Deneb. Somewhat farther down from Vega toward the southeast is Altair.

    Use binoculars in bright twilight.

    With binoculars, watch Spica join in with Venus, Mercury, and Mars as the planets go through their evolving positions.

    Sky & Telescope diagram

    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 foldout 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).

    Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of maps; 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 even more detailed 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? 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, they wisely say, "the sky never becomes a friendly place."

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

    This Week's Planet Roundup

    Mercury (about magnitude 0) is 3° or 4° lower left of much-brighter Venus, low in the west-southwest in bright twilight, as shown at the top of this page. Bring binoculars.

    Venus (magnitude –3.8) is still low in the glow of sunset. Look for it above the western horizon about 30 minutes after sundown. Fainter Mercury is just to its lower left, as shown at the top of this page. Look too for even fainter Mars.

    Mars (a dim magnitude +1.7!) is closing in on Venus from the upper left. It passes 1/3° south (lower left) of Venus on September 11th, then moves farther down to the lower right. See the illustration at the top of this page — and use binoculars! Spica, magnitude +1.0, is also nearby.

    The Great Red Spot was on Jupiter's central meridian when Christopher Go took this image at 13:19 UT August 27, 2008. The central-meridian longitude (System II) was 128°. Note the reddish Oval BA to the Red Spot's upper left, and the bright white point marking the start of a new rift in the dark North Equatorial Belt (below center). A more extensive white disturbance has developed in the North Equatorial Belt on the other side of the planet. South is up, to match the south-up view in many telescopes.

    Christopher Go

    Jupiter (magnitude –2.5, in Sagittarius) shines bright and steady in the south right after dark, and lower in the southwest later. It's above the Sagittarius Teapot and just below the smaller, dimmer Teaspoon.

    Saturn is hidden behind the glare of the Sun.

    Uranus and Neptune (magnitudes 5.7 and 7.8, respectively, in Aquarius and Capricornus) are well up in the southeast during evening. Use our online article and finder charts, or see the September Sky & Telescope, page 63.

    Pluto (magnitude 14.0, in the northwestern corner of Sagittarius) is in the south-southwest right after dark. If you've got a big scope and a dark sky, use our article and finder chart.

    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 (known as UT, UTC, or GMT) minus 4 hours.

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