by Geoff Chester, USNO Public Affairs | 27 August 2024 Messier 11, the "Wild Duck Cluster" in Scutum, imaged 2013 August 8 with an 80 mm (3-inch) f/6 Antares Sentinel refractor and a Canon EOS Rebel T2i DSLR from Fishers Island, New York. Note the density of the Milky Way star cloud! The Moon wanes through her crescent phases this week as she passes through winter’s rising constellations in the pre-dawn hours. She begins the week in the company of bright Jupiter and ruddy Mars, providing a fine photo opportunity for early risers on the 28th. On the morning of the 30th you will find Luna in a line with the stars Castor and Pollux in Gemini. New Moon occurs on September 2nd at 9:56 pm Eastern Daylight Time. It’s time for the August observing campaign for the Globe at Night citizen-science project, which runs through the evening of September 4th. This month’s featured constellation is Cygnus, the Swan, which is high overhead at around 10:30 pm local time. It is one of the sky’s most distinctive constellations, visible from most suburban locations and a real showpiece for dark-sky viewers. It has a wide range of star magnitudes, so you should be able to get a good reading on your local sky brightness to report on the web app. September 1st is the beginning of “meteorological autumn”, and if past experience means anything, the hazy, muggy nights of the past few months will be replaced by milder and drier nights, perfect for stargazing. It is my favorite time of year to take in the summer constellations and to get a preview of the stars of fall. Even my urban sky at home seems a bit clearer, and when I venture out to darker sites the star clouds of the Milky Way seem to have a bit more “pop”. The earlier times of sunset mean that I can set up my telescope before dinner and enjoy a few hours of casual observing before turning in for the night. There are also many interesting objects to look at. During the course of these evenings it’s possible to see colorful double stars, glittering galactic star clusters, the star swarms of globular star clusters, glowing gaseous nebulae, and even distant galaxies millions of light-years from the Milky Way itself. I like to start my telescopic “sweeps” among the stars of the Summer Triangle, which ride overhead at the end of evening twilight. Starting at Deneb, the brightest star in Cygnus, the Swan, panning the telescope to the center of the Triangle brings vast star clouds into view before reaching Albireo, perhaps the most colorful double star in the sky. I like to call it the “Navy Double”, since its components shine with blue and gold tones. Panning from Albireo to Altair, the southernmost star in the Triangle, look for a curious asterism known as the “Coathanger”, consisting of a straight line of six stars with a prominent “hook” of three stars hanging from the center of the line. It lies in the obscure constellation of Vulpecula, the Fox, and has probably been “accidently discovered” by generations of new telescope owners. Continuing southward along the Milky Way we pass through another obscure constellation, Scutum, the Shield. At the bottom of a “U”-shaped group of faint stars you may notice a smudge of light in a low-power eyepiece. Increasing the magnification will reveal one of the best star clusters in the sky, Messier 11. Its popular name is the “Wild Duck Cluster” thanks to a description of it by a 19th Century British amateur astronomer. Continue following the Milky Way to the horizon and you will pass some of the sky’s most famous gaseous nebulae with such prosaic names as the Eagle Nebula, the Swan Nebula, and the Lagoon Nebula. These are vast star-forming regions, many of which have glittering star clusters embedded in them. It’s a fun tour to take with any telescope. By September 1st the yellow glow of Saturn rises in the southeast at around 8:00 pm, and by 11:00 pm he’s easily found among the dim autumnal constellations. The planet’s rings are now tipped at a slight angle toward us as the Saturnian equinox approaches next year. What we lose in the rings’ glory we gain a bit by making Saturn’s fainter icy moons somewhat easier to see. Jupiter rises shortly after midnight, followed half an hour later by ruddy Mars. They are both high in the eastern sky as morning twilight gathers. Mars is steadily pulling eastward from Old Jove, but both planets will be prominent in the evening sky this upcoming winter. Right now Jupiter is much brighter than the red planet, but by mid-January Mars will be almost as bright as his hulking compatriot.