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The Sky This Week, 2017 August 21 - 28

One year on...
The The Total Solar Eclipse of August 21, 2017, imaged from Smith's Ferry, Idaho
Composite of 8 exposures made with an 80-mm (3.1-inch) f/6 Antares Sentinel refractor telescope
iOptron Cube Pro mount, and a Canon EOS Rebel T2i DSLR.

The Moon brightens the overnight hours this week as she waxes through her Full phase.  As the week progresses she begins to climb northward along the ecliptic, passing bright ruddy Mars as she crosses into the barren starfields of the autumnal constellations.  August’s Full Moon is popularly known as the Corn Moon, Grain Moon, and the Sturgeon Moon.  Whichever name you choose, the event occurs on the 26th at 7:56 am Eastern daylight Time.  You’ll find Luna just east of Saturn on the evening of the 21st; on the 22nd and 23rd you’ll find her flanking Mars.

One year ago millions of people were treated to the spectacle of a total solar eclipse that spanned the U.S. mainland from Oregon to South Carolina.  It has been said that this was probably the single most widely observed astronomical event in history, and from my direct experience I have no reason to doubt that claim.  The place where I chose to view the eclipse, Smith’s Ferry, Idaho, saw its population increase from 70 to over 3000 people by the time the Sun rose on the 21st.  Fortunately the weather across the country was favorable, and almost everyone along the path of totality experienced the ghostly darkness of the Moon’s shadow.  I have been fortunate to have now witnessed five of these amazing events, and I cannot think of any other natural phenomenon that comes close to watching the Sun disappear in the middle of the day.  So many phenomena take place during the few short minutes of totality that it is almost impossible to keep up with them.  In addition to the rapid changes in lighting and temperature, the effects on birds and animals is also remarkable.  Prior to 2017 the last total eclipse to cross any part of the “lower 48” occurred in 1979.  Thankfully we won’t have to wait quite as long for the next one.  On April 8, 2024 our next total solar eclipse will trace a path of totality from south Texas northeastward across the central Mississippi Valley, then across Lakes Erie and Ontario before traversing northern New England.  If you miss that one you’ll have to wait until August 12, 2045 to see the next one to touch the mainland.

The bright Moon washes out most of the fainter stars, especially those that make up the dim constellations of autumn.  Trying to identify these star patterns on a dark night is hard enough, but for most of this week they are effectively invisible.  You can still enjoy the bright glow of Arcturus, a signature star of spring evenings, which perches high in the west after evening twilight fades, and the bright stars of the Summer Triangle, nearly overhead at 10:00 pm local time.

Venus continues to slide eastward along the ecliptic.  Her path now takes her further south of the celestial equator, and if you’ve been watching her for the past several months you’ll see that she’s slowly sinking toward the western horizon.  This week she closes in on the bright springtime star Spica, and by the end of the week she’ll be just over three degrees west of the star.  Venus will zoom past Spica next week.

Jupiter hangs tough in the southwestern sky as evening twilight fades.  He is also moving eastward along the ecliptic, albeit at a slower pace than Venus.  The giant planet is now inching away from the second-magnitude star Zubenelgenubi, brightest star in the obscure constellation of Libra, the Scales.   You should still be able to get a decent view of him in the telescope during the early part of the evening.

You’ll find Saturn just west of the Moon on the evening of the 21st, when the ringed planet crosses the meridian at around shortly after 9:00 pm.  He has nearly reached the end of his retrograde loop against the stars, resuming direct eastward motion after the first week of September.  He’s at his best for observing in the evening hours, but you’ll need a good view of the southern horizon to get the best looks at him.

Mars continues to outshine all the planets except Venus, and his distinctive reddish tint makes him very obvious in the southeast evening sky.  The red planet crosses the meridian at around 11:00 pm, so you have lots of time to view him through the telescope.  The huge dust storm that has obscured the planet’s surface over the past several weeks is finally beginning to clear up, and surface features are becoming easier to see. 

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