The Sky This Week, September 2 – 9, 2014 !

The Sky This Week, 2014 September 2 – 9

Harvest Moon time!
M4_140705_01small.jpg
Globular Cluster Messier 4 in Scorpius, with the bright star Antares
and the smaller globular cluster NGC 6144

Imaged from Morattico, Virginia, USA
with an 80mm (3.1-inch) f/6 Antares Sentinel refractor and Canon EOS Rebel T2i DSLR

The Moon brightens the evening and overnight hours this week, starting off among the southerly stars of summer before entering the vast dim starfields of the autumnal skies.  Full Moon occurs on the 8th at 9:38 pm Eastern Daylight Time.  The Full Moon that occurs closest to the Autumnal Equinox is popularly known as the Harvest Moon.  This year the Full Moon of September beats the October Full Moon by one day for this distinction.  In addition to a catchy name, the Harvest Moon also describes a phenomenon that occurs at this time of the year in which the times of successive moonrises around the time of Full Moon differ by about half an hour instead of the more usual one hour.  This effect becomes more noticeable in more northerly latitudes; residents of Stockholm in Sweden see successive moonrises just over 20 minutes later each night.  Folks in Tromsø, Norway will find Luna rising at about the same time for the nights around Full Moon; north of about 70 degrees latitude Luna actually rises earlier for several nights!  This phenomenon once assisted farmers bringing in their crops by providing the light of the rising Moon to assist them in their labors, allowing them to work late into the night.

The last few weeks of astronomical summer produce another subtle change in the night sky.  This is one of two times during the year that the length of daylight changes at its most rapid rate.  In the spring we all notice the days getting longer, and now we see the opposite effect.  Most of us notice this at the time of sunset, which occurs about two minutes earlier each day as we approach the equinox.  Since the stars set four minutes earlier each day throughout the year, the net effect is that the constellations seem to slow their passage across the sky in the fall, so the stars of summer will seem to linger with us well into November.

The bright light of the Moon will mask our view of the summer Milky Way for the week, but we can still enjoy the brighter constellations of the season.  Looking straight up at around 10:00 pm you’ll see the three bright stars of the Summer Triangle, Vega, Deneb, and Altair.  Each of these stars leads its own constellation, of which Cygnus, the Swan, is the most prominent.  The star Deneb marks the swan’s tail, while its head is shown by the third-magnitude star Albireo, which lies almost smack in the middle of the Triangle.  Albireo is a treat for owners of small telescopes, easily resolving into one of the most beautiful double stars in the sky.  Thanks to its distinctive blue and gold colors, I like to refer to it at “The Navy Double”.  Moving to the brightest star in the Triangle, Vega, use binoculars to search for a pair of fifth-magnitude stars just to the northeast.  Each component of this wide double star is itself another double, with components that require a telescope of at least three inches aperture to see.  This “double-double” is often used as a test of good optics and is a fine example of a quadruple star system.  The last of the three bright stars, Altair, has the distinction of being one of the closest first-magnitude stars to our solar system, at a distance of just 16.7 light-years.

The early evening planet parade still features Mars and Saturn, but the latter is now being left behind in the former’s wake.  You’ll have to act quickly to get a good look at the ringed planet, setting up the telescope in evening twilight to catch Saturn as soon as he emerges from the fading glow.  If you do this you’ll have a couple of hours to enjoy the view of this fascinating world before he sinks into the horizon haze.  Mars will continue to keep pace with the advancing Sun, rapidly sliding eastward toward the stars that form the head of Scorpius.  Most telescope owners will now find him to be a disappointing small pinkish dot in the eyepiece, but if you get a spate of steady air that will allow a high-power view you may still be able to spot some hazy features on this distant surface.

The early morning sky finds giant Jupiter rising at around 4:00 am, and by 6:00 am he’s well up in the eastern sky.  For those of you who like observing the bright planets, Old Jove will be your morning companion throughout the fall and early winter.  Fortunately the later times of sunrise will work in your favor; even now you can observe him at what I think of as a “civilized” hour.  Look for bright Venus if you’re up by 6:15 am.  The dazzling planet will be just under 10 degrees above the horizon at this time.  Try to make an effort to spot her in binoculars on the morning of the 5th.  On that day she will be less than a degree north of the bright star Regulus for one of the closest planet/star conjunctions of the year.

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