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The Sky This Week, 2017 October 3 - 10

Solace in the light of the Moon
Gibbous Moon, imaged 2017 October 3, 01:17-01:27 UT
from Alexandria, Virginia by Geoff Chester
Composite of 6 images made with an Explore Scientific AR102
4-inch f/6.5 refractor and Canon EOS Rebel T2i DSLR.

The Moon brightens the overnight hours for much of the week. The Full Harvest Moon occurs on the 5th at 2:40 pm Eastern Daylight Time, and Luna’s nearly-full face graces the evening sky for a couple of nights surrounding that date. During the later evenings in the week she wanes through her gibbous phases, reaching Last Quarter on the morning of the 12th. During the course of the week Luna moves from the barren starfields of the autumn sky to a position among the rising stars of winter. Look for her stationed above the bright stars of Orion, the Hunter during the gathering morning twilight of the 10th and 11th.

The Full Moon is often thought of as a bane to the serious stargazer since her bright light renders even the most rural sky almost as bright and devoid of stars as those above urban centers. Normally I don’t spend as much time with the telescope during these bright nights, but the events of the past couple of weeks have led me to spend more time in the yard being transported to distant places through my personal portal to the sky. I found myself spending most of last night quietly looking at the Moon, noting not only the steadfastness of her features but also the slow change of light along the terminator causing shadows to reveal subtle details in formations that I have known for many years. For a brief time I was lost in another place, disconnected from the tribulations of the Earth, absorbed in moonlight.

The bright skies are not totally devoid of sights to enjoy. The early evening offers the bright stars of the Summer Triangle asterism floating serenely overhead. The three stars, Vega, Deneb, and Altair, are the brightest members of their respective constellations of Lyra, Cygnus, and Aquila, but the star patterns themselves become hard to see due to moonlight. Smack in the middle of the triangle is a third-magnitude star called Albireo that to the naked eye is otherwise quite nondescript, but time and again I find myself slewing the telescope in its direction. Albireo is a double star as seen through the eyepiece, and it is known doe the fine color contrast between its two components. These colors are much more apparent in small telescopes, and my best views are through my 3- and 4-inch refractors. Last night I was particularly aware of the colors, which are decidedly blue and yellow-gold. Enjoy a view of them in your telescope the next time you’re out under the early autumn sky.

Jupiter has slipped into invisibility in the early evening twilight leaving Saturn as the sole bright evening planet. You’ll find him low in the southwestern sky as twilight deepens, and he sets about two hours after the end of evening twilight. We are now at the time in Saturn’s orbit when the planet’s rings are tipped at their maximum toward the Earth. For the next several years the rings will slowly tilt away from our line of sight, becoming edge-on in March of 2025.

Venus and Mars start the week in a close conjunction, with minimum separation occurring on the morning of the 5th. Use binoculars to locate Mars just a quarter of a degree from Venus in the gathering twilight on the morning of the 5th. Venus won’t linger near the red planet for long; by the end of the week Mars will trail his more dazzling rival by 3.5 degrees.