Sky at a Glance | June 29th, 2007

Some daily events in the changing sky for June 29 – July 7.

Looking west in twilight
Don't miss Venus and Saturn less than 1° apart on June 30th and July 1st. Regulus looks on from their upper left. Later in the week, Saturn moves off to Venus's right.
Sky & Telescope diagram

Friday, June 29

  • 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 10:09 p.m. Eastern Daylight Time. This season, the red spot is more easily detectable in a telescope than it has been for years. A light blue or green filter helps. (For the times of all Red Spot transits this month, visible worldwide, see the July Sky & Telescope, page 52.)

    Saturday, June 30

  • Full Moon (exact at 9:49 a.m. EDT). In the time zones of Europe and Asia this is the second full Moon in the calendar month, sometimes called a "blue Moon."

  • Venus-Saturn conjunction! This evening in twilight, Venus and Saturn appear their closest together (0.7°) as seen from the Americas. They'll fit together in the field of view of most telescope eyepieces that give a magnification of 50x or less. But how much dimmer the surface of Saturn appears than the dazzling crescent of Venus! This is because Saturn is almost 13 times farther away from the Sun — so it's lit by sunlight that's only 1/160 as bright.

    Sunday, July 1

  • This evening Venus and Saturn are still only 0.8° apart (at the time of dusk for the Americas). See the illustration above.

  • Jupiter's Red Spot transits around 11:47 p.m. EDT.

    Monday, July 2

  • Have you ever tracked an eclipsing binary star all the way through eclipse? Tonight, if you're in North America, you have a shot at SZ Herculis high overhead dipping from magnitude 10.5 to 12 and back. See the article, finder chart, and timetable in the July Sky & Telescope, page 58.

    Tuesday, July 3

  • Jupiter's Red Spot transits around 1:25 a.m. Wednesday morning EDT.

    Wednesday, July 4

  • Waiting for the fireworks to start at nightfall? Pass the time by showing friends and family the three bright evening planets: Venus low in the west, dimmer Saturn just a little to Venus's right, and Jupiter higher in the southeast — with Antares to its lower right. So many people think you can't see planets unless you own a telescope!

  • Jupiter's Red Spot transits around 9:17 p.m. EDT.

  • Winter begins in Mars's northern hemisphere.

    Thursday, July 5

  • If you've got a telescope, you probably know about the constellation Hercules overhead and its showpiece globular star cluster M13. But what else have you explored here? Check out Sue French's Deep-Sky Wonders column about the many sights near the head of Hercules in the July Sky & Telescope, page 62.

    Friday, July 6

  • Earth is at aphelion, its farthest from the Sun for the year — 3.4% farther than we are at perihelion in January.

  • Jupiter's Red Spot transits around 10:55 p.m. EDT.

    Saturday, July 7

  • Bright Venus, low in the west in twilight, is now roughly midway between Saturn (to its right) and Regulus( to its upper left).

  • Last-quarter Moon (exact at 12:54 p.m. EDT).

    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 standard is Sky Atlas 2000.0) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion or the enchanting though dated Burnham's Celestial Handbook). Read here how to use them most effectively.

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

    This Week's Planet Roundup

    Mercury is hidden in the glare of the Sun.

    Venus (magnitude –4.6, in Leo) is the brilliant "Evening Star" rather low in the west during twilight. It's having a conjunction with fainter Saturn as the week opens, then Saturn slides off to Venus's right in the days following. Both planets, meanwhile, are sinking lower in the dusk. In a telescope, watch as Venus wanes to a more and more spectacular thin crescent.

    Mars (magnitude +0.7, in Aries) is gradually getting higher in the eastern sky before dawn. But in a telescope, Mars is still just a tiny 6 arcseconds wide.

    Jupiter on June 5, 2007
    Jupiter's Great Red Spot is rotating into view around Jupiter's celestial east (following) limb in this June 5th image by Christopher Go. Note the very dark red dot, tiny but persistent, to the Great Red Spot's right in the south component of the now-divided South Equatorial Belt. Large white ovals populate the latitude of the South South Temperate Belt. The festoon activity in the Equatorial Zone continues to show weird variety. North is up.

    Jupiter (magnitude –2.5, in southern Ophiuchus) is a month past opposition. It glares in the southeast to south during evening — you can't miss it. Antares, less bright, sparkles 5° or 6° to Jupiter's lower right. The two will remain evening companions all summer.

    Saturn (magnitude +0.6, in Leo) begins the week in a lovely close conjunction with Venus, then moves off to Venus's right, as described above. Dimmer Regulus, meanwhile, is moving in from the upper left. Higher above them is 2nd-magnitude Gamma Leonis.

    Uranus (magnitude 5.8, in Aquarius) and Neptune (magnitude 7.9, in Capricornus) are well up in the southeast and south, respectively, before the first light of dawn.

    Pluto (magnitude 13.9, in the northwestern corner of Sagittarius) is not far from Jupiter in the south in late evening. Finder charts for Uranus, Neptune, and Pluto are in the July Sky & Telescope, page 60.

    All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's midnorthern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (UT, UTC, or GMT) minus 4 hours.

    To always get the up-to-date Sky at a Glance, bookmark this URL:
    http://SkyTonight.com/observing/ataglance .

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