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This is the Griffith Observatory Sky Report through September 19th, 2018. Here’s what’s happening in the skies of southern California.
The moon waxes from crescent to first quarter on the 16th, and then it is gibbous until it reaches full moon on the 24th. The time of moonset advances from 7:21 p.m. on the 12th to 1:38 a.m. on the 19th.
The moon’s eastward motion against the backdrop of the stars brings it close to each of the four bright planets now visible after sunset. The moon is 9 degrees to the upper right of the brightest planet, Venus, on the 12th. On the 13th, the moon passes three degrees above Jupiter, the second brightest of the four planets visible after sunset. On the 16th and 17th, the moon appears to move from the right to the left side of Saturn, the faintest of the quartet of bright planets. Finally, the moon is four degrees above orange Mars on the 19th. The moon and planets are currently featured through the public telescopes at Griffith Observatory.
By 8:00 p.m., in addition to the moon and planets, a number of stars are also bright enough to get our attention. In the southwest sky, below the imaginary line connecting Jupiter and Saturn, is the orange star Antares in the constellation Scorpius the Scorpion. The moon will be above Antares on the 15th. In the west, the even brighter orange star Arcturus, in Boötes the Herdsman, shimmers far to the left of the Big Dipper. It is along an arc extended to the left from the Big Dipper’s handle.
Nearly equal to Arcturus in brightness, but shining with a blue-white gleam, the star Vega, in Lyra the Lyre, appears overhead. It is part of a trio of stars called the “Summer Triangle” that includes Deneb, to the west of Vega in Cygnus the Swan, and Altair, to the south of Vega and Deneb, in Aquila the Eagle.
At 5:00 in the morning, different stars are in view. Three of them are key in locating the comet Giacobini-Zinner, now departing after its closest approach to the Earth and the sun on September 10th. The stars to find include brilliant Capella, a yellow star that is the brightest member of Auriga the Charioteer. Below Capella are a pair of bright stars, Castor, above its partner, Pollux. Castor and Pollux are the brightest stars of Gemini the Twins. Giacobini-Zinner crosses the imaginary border from Auriga to Gemini on September 13, and it is south of the mid-point of the line connecting Cappella and Castor. Now that you have a rough idea where to look for it, grab your binoculars and head to a dark location in the mountains or desert. After the moon sets, use your binoculars to look for the oval glowing head and slender tail of the comet at the location indicated on Bob King’s finder chart included in his Sky and Telescope web page. Note that the comet will be in front of the beautiful and photogenic star cluster M 35 on Saturday morning, the 15th.
A little later in the morning of the 15th, the final launch of a ULA Delta II rocket, from Vandenberg Air Force Base, should be visible from much of southern California as it arcs through the western sky. The rocket, carrying a NASA polar ice research satellite, is scheduled to launch within a 40 minute-long period that starts at 5:46 a.m. If it launches before sunrise, it should be easy to see against the dawn sky. The launch will be covered online by NASA TV.
Free views of the Sun during the day and of the moon, planets, and other celestial objects at night are available to the public in clear weather through Griffith Observatory’s telescopes from Tuesday through Sunday, before 9:30 p.m. Check our website for the schedule. The next free public star party on the grounds of Griffith Observatory, hosted by the Los Angeles Astronomical Society, the Sidewalk Astronomers, and the Planetary Society, will take place on Saturday, September 22nd.
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From Griffith Observatory, I’m Anthony Cook, and I can be reached at griffithobserver@gmail.com.