by Geoff Chester, USNO Public Affairs | 03 October 2023 The Moon and Jupiter, 2023 October 2, 03:21 UT Imaged from Alexandria, Virginia with a Canon EOS Rebel SL2 DSLR The Moon wanes in the morning sky this week, arcing high along the ecliptic as she passes through the stars of the Great Winter Circle as morning twilight begins. Last Quarter occurs on the 6th at 9:40 am Eastern Daylight Time. Luna stands high above the striding figure of Orion before dawn on the 5th. On the 7th, she passes just a degree south of the bright star Pollux, one of the Twin Stars of Gemini. The week’s best photo opportunity will be on the morning of the 10th, when the Moon passes between the stars Regulus and Algieba, the brightest stars in the “head” of Leo, the Lion while dazzling Venus lies just two degrees south of Regulus. The October observing campaign for the citizen-science Globe at Night program kicks off on the evening of the 4th and lasts through the 13th. This month’s target constellation is Cygnus, the Swan, a staple for summer and early autumn stargazers. Cygnus is very well placed for viewing during the early evening hours, passing through the zenith between 8:00 and 9:00 pm local time. Its brightest star, Deneb, is the northernmost and faintest star in the Summer Triangle asterism, and to the ancient Greeks marked the Swan’s tail. Suburban observers should have little trouble finding the principal stars of Cygnus. They form a distinctive cross-shaped pattern that, with a little imagination, depicts a passable stick figure of a swan flying through the heart of the Triangle. Darker skies will reveal more stars that seem to flesh out the Swan, and you may even catch a glimpse of the Milky Way on a cool, clear night. No matter where you live, report your observations of Cygnus via the Globe at Night web app. All observations are welcome and needed to map the spread of light pollution that is rapidly intruding on the night sky. Here in the Washington, DC area you can have a good view of the Milky Way and its celestial treats at the annual Star Gaze, sponsored by the Northern Virginia Astronomy Club. This event takes place at C.M. Crockett Park near Midland, Virginia, about 16 miles southeast of Manassas on the 7th from 5:00 until 11:00 pm EDT. Not only will you get a taste of a dark night sky, you will have the benefit of dozens of members of the astronomy club sharing their telescopes and expertise in the field of amateur astronomy. There is a park entry fee, but the program itself is free. This is a good week to look for another geometric asterism as the Summer Triangle heels to the west in the later evening hours. By 10:00 pm you should be able to see a large square of second-magnitude stars that form part of the constellation of Pegasus, the Flying Horse of Greek mythology. In one myth, Pegasus sprang from the body of the Gorgon Medusa after Perseus beheaded her. Perseus then rode the steed to the rescue of Andromeda. This is the myth that is depicted in our sky. Andromeda, her vain mother Cassiopeia, Perseus, and Medusa are fixtures in our autumnal sky. From a dark site the “Great Square” of Pegasus is joined by many fainter stars. Many amateur astronomers gauge the transparency of their observing sites by counting the number of stars they can see in the square. Saturn appears in the southeastern sky as evening twilight falls. The ringed planet crosses the meridian at around 10:15 pm, so you have ample time in the evenings to train the telescope on him. Few objects evoke more of a feeling of “outer space” than the view of Saturn for the first time. Most people simply shake their heads in mild disbelief, but a second glimpse is usually enough to convince them that the view is real. Giant Jupiter is steadily climbing into the evening sky, and now rises shortly after 8:00 pm. By 10:00 pm he begins to steal the limelight from Saturn, and beckons for a look through the telescope. Of all the planets, Jupiter offers the best features for owners of small telescopes. Just about any instrument should show the planet’s four brightest moons, first described by Galileo in 1610. A four-inch aperture instrument will show the dark equatorial cloud belts that flank its bright equatorial zone, and each increase in aperture will bring out progressively more detail. Occasionally you might glimpse the planet’s most famous feature, the Great Red Spot. Thought to be a persistent storm in Old Jove’s atmosphere, its size is enormous, covering a surface area equivalent to the entire surface area of Earth! Dazzling Venus and the Moon are the highlight players in the pre-dawn sky. Venus rises at around 3:30 am and should be easy to spot by 4:00. Venus is currently as bright as she can get, so she is virtually impossible to miss. Watch the Moon close ranks with her until the morning of the 10th, when they converge in the head of Leo in the pre-dawn hours.