Skylights featured on Astronomy Picture of the Day

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Skylights featured three times on Earth Science Picture of the Day: 1 , 2 , 3 , 4 .

Cassiopeia rising

Photo of the Week.. Cassiopeia, her Chair upside down, rises at right through the shutter of the 4-meter telescope at Kitt Peak, the telescope itself silhouetted against the sky at left. Peaking through openings in the telescope tube at left are Delta, Zeta, and Mu Cephei (Herschel's Garnet Star).

Astronomy news for the week starting Friday, September 3, 2004.

As August passes to September, we sense the scent of fall in the air, at least in the northern hemisphere: in the southern, they have the greening of spring. As summer fades, so does the Moon, which wanes through its last quarter on Monday, September 6, and thereafter enters the waning crescent phase and descends toward the dawn horizon. Less than two days after the quarter, the Moon passes apogee, where it is farthest from the Earth in its current round.

Oddly, though the first and third quarters have the same angular dimensions in the sky, the third is only about half as bright as the first as a result of a greater proportion of dark volcanic plains, or " maria," most of which partially fill large impact basins and are easily visible to the naked eye to make the "Man in the Moon" and other fanciful figures.

The early morning hours of Thursday the 9th sees the crescent make a nice triangle with Castor and Pollux in Gemini (the stars to the left), the Moon also topping Saturn. The following morning, Friday the 10th, is even better, with the Moon making a neat triangle with Saturn (above and to the right of the Moon) and brilliant Venus (down and to the right). That same morning, Mercury makes a very close pass to Regulus in Leo, the little planet only a fraction of a degree from the star, the pair making a difficult sight since they will be so close to the dawn horizon. Even if Regulus is not noted in morning twilight, Mercury should be nicely visible as it passes its greatest western elongation to the Sun on Thursday the 9th. Look just to the north of east as the sky brightens. Brighter than anything in the sky other than the Sun and Moon (and the occasional meteor), Venus still rises early, lofting itself above the eastern horizon around 3 AM Daylight Time.

As we enter September's evenings, the Big Dipper (the brightest portion of Ursa Major, the Greater Bear) and Cassiopeia (the celestial Queen) stand opposite each other across from the core of the sky, the North Celestial Pole (the Dipper to the northwest, Cassiopeia to the northeast), which is marked by Polaris at the end of the Little Dipper (the brightest portion of Ursa Minor, the Smaller Bear). Standing on its handle, the Little Dipper is at its best, though most of its stars are faint and require a dark sky to see. In between the Dippers, but much higher than Polaris shine the two eyes of Draco, the Dragon, and nearly overhead is bright Vega of Lyra. Grazing the northern horizon for those who live north of 45 degrees north latitude is Capella, which will shine high for us next winter, while far to the south is another Dipper, the Little Milk Dipper of Sagittarius, whose handle sticks into the broad heart of the Milky Way.
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