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The Sky This Week, 2016 March 30 - April 5

Lions and Archers and Bears, oh, my!
Jupiter, imaged on 2016 March 30 at 02:45 and 02:53.5 UT
imaged with the USNO 30.5-cm f/15 Clark/Saegmüller refractor

The Moon skirts the southern horizon in the morning sky this week, moving from the bright star clouds of the summer Milky Way into the sparse star fields of the rising autumnal constellations. Last Quarter occurs on March 31st at 11:17 am Eastern daylight Time. Luna may be found just to the north of the "Teapot" asterism in the constellation of Sagittarius, the Archer, a star pattern that we’ll see in the evening sky by late summer.

This week marks the April campaign for skywatchers who wish to participate in the Globe at Night citizen-science program that runs from now through April 8th. This month our focus constellation shifts from Orion to Leo, the Lion, which is well-placed for viewing just east of the meridian at the end of evening twilight. Leo is currently hosting the bright planet Jupiter which should help you locate it easily. Leo consists of two distinct asterisms, the "sickle" and the "Triangle". To locate the Sickle, look to the northwest of Jupiter for the first-magnitude star Regulus. Moving up from the star you’ll see a semicircle of fainter stars that make up the Sickle’s blade. If you have a small telescope be sure to look at the brightest star in the blade, second-magnitude Algeiba. This is a fine double star consisting of two gold-tinted suns separated by about five arcseconds. Use a power of about 100X to split this excellent pair. The Triangle lies almost directly above Jupiter and consists of two third-magnitude stars and the second-magnitude star Denebola. To participate in the Globe at Night star count, go to the program’s website and compare your views of Leo with the provided finder charts. The brightness of your local sky is then determined by the number of stars that you see in Leo’s vicinity. It’s an easy observation to make, and your efforts will be incorporated into a global sky-brightness database.

If you look above Leo to the northern sky you should have no trouble finding the seven stars of the "Big Dipper", an asterism made up of the brightest stars in the constellation of Ursa Major. There’s another easy double star here for the small telescope owner as well as a test for your naked-eye acuity. If you look at the star Mizar, which lies at the "bend" of the Dipper’s handle, you may see a fainter star butted up next to Mizar itself. This is Alcor, and it has been used as a test of visual sharpness for millennia. Point a telescope at this duo and you’ll see that Mizar itself is also double. This was the first non-planetary target I observed with my small 2.4-inch refractor back in 1960!

The showpiece for the evening is the giant planet Jupiter, which is now well up in the east as evening twilight fades. Old Jove is now about a month past opposition and is well-placed for prime-time viewing. You can see the planet and his four bright Galilean moons with almost any telescope; if you can hold a pair of binoculars steady enough you can just make them out as well. A three-inch telescope should show the planet’s two dark equatorial cloud belts, and each increase in aperture will bring out more detail. A six- to eight-inch telescope should begin to resolve the moons into tiny discs, and careful scrutiny at higher magnifications will show individual storms, swirls, and dark spots in the planet’s streaky cloud belts. From the eastern U.S. you can watch the moon Io drag its shadow across Jupiter’s face on the evening of the 30th, and on the evening of April 3rd the famous Great Red Spot rotates across the field of view.

Mars and Saturn continue to be best placed for viewing in the pre-dawn sky. Mars now rises in the southeast at local midnight, with Saturn following an hour later. The two planets continue to form a compact triangle with the bright red-tinted star Antares in the constellation of Scorpius, with Mars the brightest of the three objects. You’ll need a very calm morning to get a good telescopic view of these planets since their far southerly declination means we’re looking through lots of Earth’s turbulent atmosphere to spy details on their distant surfaces.

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