This Week’s Sky at a Glance, August 9 – 17

 

Friday, August 9

• The waxing gibbous Moon shines near Jupiter this evening, as shown here. But Jupiter, 40 times larger than the Moon, is currently 1,830 times farther away.

Jupiter's own four big moons, roughly as big as ours, are pinpoints in a small telescope or good, steadily braced binoculars. They're lined up east and west of the planet. This evening you'll find Europa to Jupiter's east and Io, Callisto, and Ganymede to its west, counting outward. See the guide to Jupiter's moons for every night in August, good worldwide, in the August Sky & Telescope, page 51.

Saturday, August 10

• Narrow windows for good Perseid viewing. The annual Perseid meteor shower is predicted peak late on the night of August 12-13, but the waxing gibbous Moon won't set that night until just before the beginning of dawn.

You may do better a day before that, on the morning of the 12th, if you catch the hour or so of dark sky between moonset and the start of dawn (for North America). And, there's a possibility this year of a second peak in the meteor rates due right around then for North America (around 10h UT August 12th).

A day earlier on the morning of the 11th — late tonight, in other words — we get two dark hours before dawn, but the meteor rates will probably be low. However, there are indications that this year's Perseid shower is bringing some unusual early fireballs.

Not sure when dawn begins? At this time of year it's about 1 hour 45 minutes before your local sunrise time if you're in the world's midnorthern latitudes (near 40° N.)

Here's the International Meteor Organization's near-real-time graph of Perseid activity this year, based on scientific, standardized-method meteor counts coming in from visual observers around the globe.

Sunday, August 11

• The Moon shines with Saturn tonight, 3° or 4° to Saturn's right as seen during evening in North America.

Physically Saturn is 35 times as large as the Moon (not counting the rings), and tonight it's 3,500 times farther away.

Saturn's own largest satellite, Titan, is 1.5 times as large as our Moon. A small or medium-size telescope shows it tonight as an 8.5-magnitude orange pinpoint, about four ring-lengths to Saturn's west.

Monday, August 12

• It's supposed to be peak Perseid night, but you'll have the bright light of the waxing gibbous Moon washing the sky, so only the brightest meteors will show through. Best time: the later in the night the better, right up to the beginning of Tuesday's dawn.

Not sure when dawn begins? It's about 1 hour 45 minutes before your local sunrise time if you're in the world's mid-northern latitudes (near 40° N.)

Tuesday, August 13

• The nights around full Moon, such as now, are traditionally considered the worst for lunar observing. But not if your interest is crater rays! These show best under high, shadowless illumination. To go exploring, see Chuck Wood's "Unruly Crater Rays" in the August Sky & Telescope, page 52. Do you know about the hill-blocked ray pattern of Kepler?

Wednesday, August 14

• Full Moon tonight and tomorrow night. The actual moment of full Moon is 8:29 a.m. tomorrow morning EDT. So for evening skywatchers in the time zones of the Americas, both this evening and tomorrow evening qualify as "full moon" about equally.

Tonight the Moon is in dim Capricornus. Tomorrow it'll be just across the constellation border into dim Aquarius.

Thursday, August 15

• Different people have an easier or harder time seeing star colors, especially subtle ones. To me, the tints of bright stars stand out a little better on a bright sky background — such as we have with the moonlight tonight.

For instance, the two brightest stars of summer are Vega, overhead soon after dark, and Arcturus, shining in the west. Vega is white with just a touch of blue. Arcturus is a yellow-orange giant. Do their colors stand out a little better for you in moonlight or in late twilight?

Binoculars, of course, always make star colors easier.

Friday, August 16

• As August proceeds and nights begin to turn chilly, the Great Square of Pegasus lifts up in the east, balancing on one corner. Its stars are only 2nd and 3rd magnitude, and your fist at arm's length fits inside it. Late this evening the waning gibbous Moon rises below it.

From the Square's left corner extends the main line of the constellation Andromeda: three stars (including the corner) about as bright as those forming the Square.

This whole giant pattern was named "the Andromegasus Dipper" by the late Sky & Telescope columnist George Lovi. It's shaped sort of like a giant Little Dipper with an extra-big bowl, and it's currently raising its contents upward.

Saturday, August 17

• The actual Little Dipper, meanwhile, is tipping far over leftward in the north. It's less than half as long as the Andromegasus Dipper, and most of it is much fainter. As always, you'll find that it's oriented more than 90° counterclockwise compared to Andromegasus.

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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.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) and 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, or the bigger Night Sky Observer's Guide by Kepple and Sanner.

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). And 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."

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This Week's Planet Roundup

Mercury displays itself low in early dawn this week as it brightens from magnitude –0.2 to –0.8. Use binoculars to look for it very low about 45 minutes before sunrise. It's below or lower right of twinklier Pollux and Castor, as shown here. Don't confuse it with Procyon off to its right.

Venus and Mars are out of sight behind the glare of the Sun.

Jupiter (magnitude –2.3, between the feet of Ophiuchus) is the white dot in the south as twilight fades. Jupiter starts getting lower in the south-southwest soon after dark. Orange Antares, much fainter at magnitude +1.0, twinkles 7° to its lower right.

Jupiter and Antares form a shallow, nearly isosceles triangle with Delta Scorpii (Dschubba) to their right. Delta, a long-term eruptive variable of the Gamma Cassiopeiae type, has been only a little fainter than Antares for most of the last 19 years — after it brightened by some 50% in July 2000.

In a telescope Jupiter is 41 arcseconds wide and shrinking gradually. See Bob King's observing guide to Jupiter.

Saturn (magnitude +0.2, in Sagittarius) is the steady, pale yellowish "star" in the south-southeast during and after dusk, 30° left or upper left of Jupiter. Below Saturn you'll find the handle of the Sagittarius Teapot.

Uranus (magnitude 5.8, in Aries) is high in the southeast before the beginning of dawn.

Neptune (magnitude 7.8, in Aquarius) is well up in the southeast by 11 or midnight and highest in the south well before dawn. Finder charts for Uranus and Neptune.

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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, GMT, or Z time) minus 4 hours.

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Audio sky tour. Out under the evening sky with your earbuds in place, listen to Kelly Beatty's monthly podcast tour of the heavens above. It's free.

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“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