This Week’s Sky at a Glance, August 14 – 22

 

Friday, August 14

• This is the time of year when the Teapot of Sagittarius, with its rich surroundings of deep-sky objects, stands highest in the south soon after dark. The Teapot is about the size of your fist at arm's length. It's tipping and pouring to the right, as seen below.

The Sagittarius Teapot deep-sky and surroundings.

The Large Sagittarius Star Cloud seems to emerge like steam from the spout of the Sagittarius Teapot. In reality, it's far in the background.

Saturday, August 15

• Spot Saturn in the southwest after dark. The brightest star left or lower left of it is orange Antares. The star more or less between the two is Delta Scorpii, a blue-white-hot variable star. It unexpectedly doubled in brightness in July 2000 and has remained bright, with fluctuations, ever since.

Draw a line from Antares through Saturn, extend the line almost as much farther on, and you hit fainter Beta Librae (Zubeneschamali). Much farther on, you come to Arcturus.

Moon and Mercury at dusk, Aug. 16-17, 2015

The thin waxing Moon is beginning to return to the evening sky. Use it to spot Mercury, very low. Bring binoculars; the visibility of objects in bright twilight is exaggerated here.

Sunday, August 16

• In bright twilight, scan with binoculars very low in the west for Mercury about 6° to the right of the thin crescent Moon, as shown here.

Monday, August 17

• After sunset, the waxing crescent Moon low in the west serves as a pointer to Mercury, well to its lower right as shown here. If the Moon were a bow, it would shoot an arrow through Mercury.

• The two brightest stars of summer are Vega, overhead soon after dark, and Arcturus in the west. Vega is a white-hot, type-A star 25 light-years away. Arcturus is a yellow-orange-hot K giant 37 light-years distant. Their color difference is easy to see.

Tuesday, August 18

• As night descends, look left of the Moon for Spica. Very high above the Moon shines brighter Arcturus.

• The red long-period variable star Chi Cygni is still about at maximum light. As of August 14th it was about magnitude 4.7. See the article and comparison-star chart in the August Sky & Telescope, page 51.

Wednesday, August 19

• Look a few degrees below the Moon at dusk for twinkly Spica.

Thursday, August 20

• The Moon this evening is nearly halfway between Spica, to its lower right, and Saturn, to the Moon's left or upper left.

Friday, August 21

• The bright "star" left of the Moon this evening is the planet Saturn. Lower left of Saturn sparkles fainter Delta Scorpii. Farther left or lower left from there is the orange-red supergiant Antares.

Saturday, August 22

• First-quarter Moon (exact at 3:31 p.m. EDT). As dusk fades, the Moon shines near Saturn and Beta (β) Scorpii, as shown below. Beta is fine telescopic double star. So is Nu Scorpii, upper left of Beta by 1.6°. (Nu is a little too faint to get on the chart.)

Moon passing stars, Aug. 22-25, 2015

In the coming week, watch the Moon wax its way eastward above Scorpius, then Sagittarius. The blue 10° scale is about the size of your fist held at arm's length.

__________________________

Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. 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 guide to astronomy.

Pocket Sky Atlas

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's still less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae.

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 the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). 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

Venus 7 days from inferior conjunction, imaged by Damian Peach.

Venus a week before inferior conjunction. Damian Peach shot this image in broad daylight on August 8th, using a 900-nm infrared filter on his 14-inch scope. Imaging in infrared "greatly helped with contrast," writes Peach. "The scope aperture was also masked down to prevent stray light entering." Venus was 13° from the Sun.

Saturn on July 18, 2015

Saturn as imaged by Christopher Go on July 18th. South is up. For small scopes, the most apparent feature on the globe is the contrast between the bright Equatorial Zone and the darker North Equatorial Belt.

Mercury (about magnitude –0.2) is very low due west in bright twilight; this is a poor Mercury apparition for the Northern Hemisphere. About 20 minutes after sunset, scan for it just above the horizon with binoculars or a wide-field telescope.

Venus is out of sight this week. It goes through inferior conjunction (between us and the Sun) on Saturday the 15th. Venus will miss the Sun by a wide margin at this conjunction, passing nearly 8° to the Sun's south.

Mars (a mere magnitude +1.7) is low in the glow of dawn. Look for it low in the east-northeast about 45 minutes before sunrise. Don't confuse it with Pollux or Castor above it, or brighter Procyon off to its right.

Jupiter is lost in the sunset.

Saturn (magnitude +0.5, in Libra) shines in the south-southwest at nightfall, to the right of upper Scorpius. Fiery orange Antares, less bright, twinkles 13° to Saturn's left or lower left. Delta Scorpii shines more or less between them.

Uranus (magnitude +5.8, in Pisces) and Neptune (magnitude +7.8, in Aquarius) are well up in the southeastern sky by midnight. Finder charts for Uranus and Neptune.

__________________________

All descriptions that relate to your horizon — 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) is Universal Time (UT, UTC, or GMT) minus 4 hours.

__________________________

“This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours.”

— Neil deGrasse Tyson, 2014