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The Sky This Week, 2017 October 24 - 31

A great week to observe the Moon!
The Moon at First Quarter, 2016 NOV 7, 22:42 UT
imaged from the U.S. Naval Observatory, Washington, DC by Geoff Chester
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor
and Canon EOS Rebel T2i DSLR.

The Moon waxes in the evening sky this week, reaching the First Quarter phase on the 27th at 6:22 pm Eastern Daylight Time. Luna begins the week just east of Saturn, then ventures into the dim stars of the autumnal constellations.

The evening of the 28th has been designated as "International Observe the Moon Night", an evening devoted to exploring the myriad features of our only natural satellite. The Moon will be on the meridian at around 8:00 pm, and the terminator (the line dividing day from night on the lunar sphere) will be ideally placed to reveal some of the Moon’s most famous features. Organized public observing events in the Washington metro area include viewings at the Phoebe Wasserman Haas Public Observatory at the National Air & Space Museum on the Mall. Amateur astronomers will also be convening at Fort Washington National Park with telescopes to share the view. If you happen to have a telescope, set it up on Saturday evening and share the view with your friends and neighbors. Luna’s surface, just under a quarter of a million miles away, is the only place in our universe other than the earth where you will find human footprints. While you won’t see the Apollo landing sites through any terrestrial telescope, you can nonetheless explore the barren beauty of the Moon’s many varied landscapes with very modest optical aid. While these features have remained essentially unchanged for the duration of human history, they always present a slight difference in lighting and detail from lunation to lunation. The Moon is often "looked over, then overlooked" by astronomers, yet it remains the single easiest celestial object to observe, as visible to city-bound telescopes as it is to those on remote mountain peaks. Visit the event’s website for resources, including a map of Luna’s basic features that will be visible on the 28th.

October 31st marks one of my favorite annual observances, Halloween. It seems that each year the decorations that people put up for this event get more elaborate, and the number of ghosts, goblins, and other masked young revelers seems to grow exponentially. Whether they realize it or not, people are actually observing an astronomical event known as a "cross-quarter" day, one that marks the halfway point between astronomical seasonal dates of solstices and equinoxes. These dates have been observed in many traditions for centuries, and have gradually been assimilated into modern popular culture. Halloween was derived from an ancient Celtic pagan ritual observance of the end of the harvest season and the beginning of the dark days of winter. At this time it was believed that the boundary with the underworld became more transparent, allowing departed spirits to invade the conscious world. Under the influence of Christianity it became a feast observing the passing of saints, martyrs, and others who died in the faith, rewarding their souls with sustenance for the coming year. This year we can extend the spirit of Observe the Moon Night; set your telescope up and offer a view of the Moon as one of your treats for the roving spirits.

Saturn will still be visible for early trick-or-treaters, so you might want to get him in the eyepiece before the ringed planet settles toward the horizon. He sets just over an hour after the end of evening twilight.

You’ll have to wait until the pre-dawn hours to find another bright planet. Ruddy Mars rises at around 5:00 am while Venus comes up about an hour later. Mars should be relatively easy to spot once Venus crests the horizon. The red planet will be about 12 degrees above Venus as the week begins. Venus will add another four degrees of separation between the two by the week’s end.

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