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The Sky This Week, 2011 October 25 - November 1

A cross-quarter celebration and Jupiter at opposition.
Cylindrical projection map of Jupiter based on images
obtained between 2011 OCT 7 & 10

20-cm (8-inch) f/10 Schmidt-Cassegrain telescope with
2X Barlow lens and DFK21AU04.AS CCD camera

The Moon returns to the evening sky this week, waxing through her crescent phases as she emerges from the twilight of the southwestern sky. First Quarter occurs on November 2nd at 12:38 pm Eastern Daylight Time. Try to spot the two-day-old crescent about half an hour after sunset on the 28th. You should be able to spot the bright glow of Venus some 10 degrees below and to the right of the Moon at this time. Over the next half hour use binoculars to locate the fleet planet Mercury, which lies only two degrees below Venus, and the ruddy star Antares, which will be six degrees to the left of the Moon.

The highlight of the week occurs on October 31st. There’s nothing really special going on in the sky that night, but it is my favorite "cross-quarter" day celebration of the year. Halloween is probably the most widely observed of these mid-season markers here in the U.S., but most of the kids (and adults) who dress up and roam the neighborhoods in search of treats probably have little or no clue to the date’s astronomical origins. To the ancient Celts this was a time celebrated as Samhain, the feast of the departing Sun and the traditional beginning of winter in northern climes. Of all the seasonal markers this was the darkest, and it became associated with the spirits of the dead in many cultures. All Saints Day (November 1st), All Souls Day (November 2nd), and Dia de los Muertos (widely celebrated in Mexico and other Latin-American traditions on the 1st and/or the 2nd) all fall at this time of year. If you want to give your costumed visitors an extra "treat" this year, set your telescope up in the yard and give them a view of the five-day-old crescent Moon. You’ll be the hit of the neighborhood!

As mentioned earlier, the bright planet Venus is joined this week by the often elusive Mercury, low in the southwest after sunset. The two objects maintain a near-constant two-degree separation all week long as they both slowly climb away from the glare of the Sun. This is not the best evening appearance for fleet Mercury, but his close proximity to dazzling Venus should make him relatively easy to find. A pair of binoculars will greatly aid your search for Mercury, which should be located below Venus for the next couple of weeks before dropping back into the twilight glow.

Jupiter reaches opposition to the Sun on the 28th. On this date the giant planet will rise at sunset and set at sunrise, which means that we are now in the peak observing season for the solar system’s largest planet. This is also when Old Jove is closest to the Earth, a mere 594 million kilometers (369 million miles) away. If you have binoculars, this is a great time to look for the four bright moons discovered by Galileo in 1610. For a couple of days on either side of opposition the moons will appear almost half a magnitude brighter than usual due to a phenomenon known as the Seeliger Opposition Effect. This is particularly apparent on the outer moons Ganymede and Callisto, whose rough surfaces lose the shadows caused by their topography during these few days.

Ruddy Mars continues to methodically drift eastward in the morning sky. For the past few clear mornings he has greeted me, along with Orion and the stars of the winter sky, as I retrieve the morning paper. The red planet halves the gap between him and the bright star Regulus in the constellation of Leo. Star and planet are quite similar in brightness, but the contrast in color between icy-blue Regulus and the rust-hued Mars becomes more apparent as the two objects draw together.

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