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The Sky This Week, 2018 July 31 - August 14

It's summer vacation time...
Night
Under the summer stars, Desolation Canyon, Utah, imaged 2018 June 21

We’ll be taking a short break for a brief summer vacation, so this edition of “The Sky This Week” will take us through the first half of August.

 

The Moon wanes in the morning sky, reaching Last Quarter on August 4th at 2:18 pm Eastern Daylight Time.  She spends the first week among the faint stars of the rising autumnal constellations, then slips through her crescent phases as she passes through the winter stars in gathering morning twilight.  New Moon occurs on the 11th at 5:58 am EDT, and by the end of the second week you’ll find her back in the evening sky, where be close to dazzling Venus in the deepening evening twilight on the 14th.  The New Moon on the 11th will produce a partial eclipse of the Sun for denizens of northern polar regions as well as a significant part of eastern Siberia and much of China.  If you happen to find yourself in the town of Pevek in Russia’s far-flung Chaunsky District you will see about 67percent of the Sun’s disc obscured by the Moon, but the event will occur very close to the horizon.  Here in Washington we’ll have to wait until June 10, 2021 to see our next solar eclipse.  It will also be a partial, with about 70 percent of the Sun’s disc covered as Old Sol rises that morning.

The next couple of weeks will provide some of the best summertime stargazing for vacationers who can get away from city lights.  This is “prime time” for viewing the splendors of the summertime Milky Way during the overnight hours.  Astronomical twilight now ends at around 10:00 pm, and by 11:00 pm the soft glow of our home galaxy can be traced from the bright star clouds in Sagittarius to the south up through the bright stars of the Summer Triangle near the zenith.  It then continues over to the northeast horizon where you’ll find the “W”-shaped constellation of Cassiopeia rising against the Milky Way’s diffuse background glow.  If there is a perfect time to pick up an interest in amateur astronomy it is during this time.  You don’t need sophisticated equipment to begin your exploration of the sky; a good pair of 7X50 binoculars will do.  Sweep your glasses over the Milky Way and you will be amply rewarded.  The misty glow will start to resolve into clouds of countless stars interspersed with tighter knots of soft-glowing light.  You can identify many of these glimmering patches with any number of smart-phone apps, but put a piece of red gel over your phone’s screen to preserve your night vision.  If you have a small telescope you can resolve these fuzzy patches into clusters of stars and softly glowing gas.  My favorite instrument for scanning these regions is my 80 millimeter f/6 refractor with a wide-field low-power eyepiece.  It shows me not only the resolved star clouds of the Galaxy, but it also reveals mysterious dark patches where no stars shine at all.  These “dark nebulae” represent molecular clouds where the building blocks of stars and planets are present.  They will eventually become clusters of bright young stars that may be visible to our distant descendants!

The annual Perseid meteor shower reaches its peak on the night of the 12th-13th.  This is the year’s most reliable and consistent meteor display, and this year there will be no interference from stray moonlight.  The shower’s “radiant”, the point in the sky from which the “shooting stars” seem to originate, lies just below Cassiopeia and climbs higher as the night passes.  The best time to view the shower is after midnight, and a single observer at a dark location can expect to see over 50 meteors per hour.  Perseids are typically quite bright and very swift, and I expect a good show this year.

Venus hangs tough in the western twilight sky.  She now sets at the end of evening twilight, so you’ll be limited to seeing her against a brighter sky.  She will get a visit from the waxing crescent Moon on the evening of the 14th. 

Jupiter may be found in the southwest as evening twilight deepens.  You don’t have too much time to catch a good view of him in the telescope, so try to get the scope on him as soon as he becomes visible.  He is slowly drifting eastward toward the star Zubenelgenubi in the constellation of Libra.  He’ll pass just half a degree north of the star by the middle of the month.

Saturn is in prime viewing position for most of the overnight hours.  He crosses the meridian at around 10:00 pm, which is when he reaches his culmination above the southern horizon.  That said, he never gets higher than 30 degrees of altitude for most of us in the mid-Atlantic, so pick a night with still air to get your best view of the planet and his magnificent rings.

Mars is now as close to the Earth as he’s going to get this year, a tad over 57,590,000 kilometers (35,784,870 miles).  This is as close as he’s been since 2003, and we will have to wait until 2035 to see him this close again.  His apparent disc is just a bit over half the size of Jupiter’s, so it’s possible to glimpse surface detail with a modest telescope.  It appears that the global dust storm that has obscured his surface is finally beginning to wane, so over the next few weeks some details might become clearer.  However, as with Saturn, Mars is low in the southern sky, so you’ll need very steady air to get a good look at him. 

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