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The Sky This Week, 2021 October 12 - 19

All eyes on the Moon!
The Moon, imaged 2021 May 22 from Alexandria, Virginia
The Moon, imaged 2021 May 22 from Alexandria, Virginia,
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor,
1.6X Antares 2-inch Barlow lens, and a ZWO ASI224MC color CCD imager.

The Moon waxes in the evening sky this week, brightening the southern horizon as she pays a visit to the giant planets Saturn and Jupiter.  Full Moon occurs on the 20th at 10:57 Eastern Daylight Time.  October’s Full Moon is widely known as the Hunter’s Moon to residents of the Northern Hemisphere.  It shares similar horizon geometry to last month’s Harvest Moon.  Just as the relatively short interval between successive moonrise events gave farmers a bit of extra illumination to bring in the harvest, this month a similar circumstance allows hunters to pursue game across the stubble of the harvested fields.  

October 16th is International Observe the Moon Night, a NASA-sponsored event intended to bring worldwide attention to Earth’s only natural satellite.  Weather permitting the gibbous Moon will be scrutinized by thousands of astronomers and casual skywatchers around the world to bring attention to our nearest neighbor in space.  You won’t need fancy equipment to participate as Luna can be enjoyed with the unaided eye as well as optical aids like binoculars and small telescopes.  If you have a telescope this presents a great opportunity to share your views with neighbors and friends.  Here in the Washington DC area you can get a jump on the event by attending the Open House at the Analemma Society’s observatory at Turner Farm Park in Great Falls, Virginia.  Beginning at 7:30 pm EDT on Friday the 15th, the observatory has four telescopes for public viewing.  In addition, many local amateur astronomers come by to share the views through their instruments.  

Why all the fuss about the Moon?  I often say that she is “Looked over, then overlooked” by newcomers to astronomical observing.  While her surface features have remained essentially frozen in time for hundreds of millions of years, subtle changes in lighting offer constant change in the way that these features appear.  Luna’s surface turns out to be an almost bewildering array of great impact basins, lava flows, craters, mountains, and sinuous channels.  All of these offer a wonderful alien landscape to enjoy from the comfort of your back yard, and it doesn’t matter if you live in the center of the city or way out in the country.  Above all, the Moon represents the most distant frontier that humans have directly explored.  While it is impossible to see the footprints, flags, and other hardware that were left behind by the 12 Apollo astronauts who walked on its surface, I can still feel their presence on that far-flung landscape that Edwin “Buzz” Aldrin called “magnificent desolation”.

The Moon’s brightening glow gradually hides the fainter stars of the autumn constellations, but there are a few bright stars that 5bright stars that still punctuate the night.  High overhead at 8:00 pm local time you can see the stars that form the Summer Triangle asterism.  Vega, Deneb, and Altair are easy to find from the city as they wheel toward the west as the night passes.  By 10:00 pm the stars that form the “Great Square” of Pegasus climb toward the zenith, and by the early morning hours the stars of the Great Winter Circle, led by the familiar figure of Orion, ascend in the eastern sky.

The dazzling planet Venus is best seen in the southwestern sky as evening twilight falls.  This week she passes just to the north of the ruddy star Antares, the heart of Scorpius, the Scorpion.  She will pass her most southerly point in this year’s apparition late next week.

Saturn gets a visit from the Moon on the evenings of the 13th and 14th.  The ringed planet crosses the meridian at around 8:00 pm, which is when he’ll be best placed for viewing in a telescope.  Check out the nearby Moon while you’re in the area.

Giant Jupiter reaches the second stationary point of the current apparition on the 18th.  He will gradually resume eastward motion over the next few weeks, putting more distance between himself and Saturn.  It will be another 20 years before the two planets will encounter each other again.  Look for the Moon near Jupiter and Saturn on the evening of the 14th.  Luna follows Old Jove on the following evening, then leaves his vicinity until next month.