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Sky Report -September 2011

Crescent Dusk Moon as Month Begins & Ends, Harvest Moon & Jupiter in East in Late PM Hours

Sky Sights all through September 2011 – The Summer Triangle is prominent all month, appearing high in the South with its long sides pointing towards the horizon. The Triangle’s lowest tip is marked by the bright star Altair, marking the eye of Aquila, the Eagle. On dark, moonless evenings in the 2nd half of September, the Milky Way can be seen as a delicate glow running across the left side of the Summer Triangle. The Triangle’s brightest star is Vega, which appears nearly overhead as darkness falls. The Big Dipper is easy to spot in the early evening hours with its scoop to the left and handle on the right. Extend the handle outward to the bright golden star Arcturus, twinkling furiously as it nears the Northwestern horizon. As the evening hours pass, two bright objects appear in the eastern half of the sky, the golden star Capella in the Northeast and the very bright planet Jupiter in the East. You can be sure that you are seeing Jupiter as it shines steadily, not twinkling as the bright stars. Close to the southern horizon is the bright star Fomalhaut, marking the mouth of the Southern Fish.

Sky Sights in Early September 2011 – On September 1, the crescent moon will appear below the bright star Spica in the western dusk. On Sunday, September 4th, the evening moon will appear half full, resembling a tilted letter ‘D’. For a few days before and a few days after September 4th, you will have the best views of the moon’s craters and mountains through binoculars and telescopes. For along the moon’s straight edge, the sun is rising, lighting up the crater rims and mountain peaks. On the evening of September 8th, the moon will appear below the bright star Altair of the Summer Triangle.

Sky Sights in Mid September 2011 – On September 11th, the moon is full, shining in western Aquarius. This is the Harvest Moon, the full moon closest to the start of fall (September 23rd). At this time of the year, the moon’s orbital path makes a low angle to the eastern horizon. As the moon moves eastward along its orbit, it also moves northward, reducing the moon’s delay in moonrise from night to night. (Ordinarily, the moon rises about 50 minutes later each night.) At full moon, the moon rises at sunset and hangs in the sky all night long. In the nights following the Harvest Moon, the moonrise is only a half hour later from night to night. This allows the moon to dominate the early evening sky for 3-4 nights after the Harvest Moon. Colonial farmers who worked their fields with hand tools could continue to harvest their crops in the early evening hours by the light of the Harvest Moon. Late on the evening of July 16th, the moon will appear to the left of the bright planet Jupiter. On September 20th, the moon will appear half full in the southern dawn sky, resembling a reversed letter ‘D’. This is another good time to view the moon’s craters and mountains with binoculars or telescope. Along the straight edge of the moon, the sun there is setting. Of course, never look at the sun with binoculars or a telescope as you could become permanently blind in a fraction of a second.

Sky Sights in Late September 2011 – Fall officially begins on September 23rd at 5:06 a.m. as the sun’s direct rays cross the equator, moving southward. On this day, the sun rises due East and sets due West. Due to the the refraction (bending upward) of the Earth’s atmosphere, daylight lasts about 8 minutes longer than night on the first day of fall. On September 26th, sunlight and night are balanced at 12 hours each. On September 27th, the moon swings from the morning to the evening side of the sun (New Moon). On September 29th, the moon may be seen as slender crescent low in the western dusk. The first sighting of the crescent moon after the start of fall marks the start of Jewish New Year, Rosh Hashanah. If you have a flat western horizon, you may also be able to spot the brilliant planet Venus below and to the right of the moon in the 7:40 p.m. dusk on September 29th.

The Frostburg State Planetarium will resume its Sunday fall programs on September 11th at 4 p.m. The September program is “Moons’ Curiosities”, all about the unusual features of the moons orbiting the planets in our solar system. Also featured is an informal tour of the Early Fall evening sky using our Planetarium projector. There are also programs at 7 p.m. These programs last about 50 minutes. The Planetarium is in Tawes 302, just off the front lobby that faces the Compton Science Center. These programs change monthly and are free to the public. No reservations are needed, just come a little bit early as once programs start, it is difficult to seat visitors in a darkened planetarium.

By Dr. Bob Doyle

To contact Dr. Doyle, his mailing address is Planetarium, Frostburg State University, Frostburg, MD 21532 or by email at rdoyle@frostburg.edu.









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