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Northern Sky: August 31 - September 13

Northern Sky Map.  Courtesy Deane Morrison.
Northern Sky Map. Courtesy Deane Morrison.

by  Deane Morrison
August 31 - September 13, 2019

Over Labor Day weekend, the moon is a young sliver that sets before or shortly after nightfall. Each night it moves farther eastward, on its monthly tour of the sky. It’s waxing brighter now, and won’t begin withdrawing from the evening sky until after the full phase in mid-September. So if you’re an evening star watcher and you go out during the two weeks after Labor Day, you’ll probably be seeing a lot of the moon.  

As for the stars, this month the Summer Triangle is high in the south, in prime position for evening viewing. The brightest of the three stars, Vega, in the constellation Lyra, the lyre, is just a hair less bright than the star you may have noticed slowly sinking in the west. That’s Arcturus, the anchor of Bootes, the herdsman, and the brightest star in the northern hemisphere of the sky. In the east, the Great Square of Pegasus, a fall constellation, is climbing into prominence.

Every year the stars and constellations are the same, but the planets move around. This summer, we’ve been treated to the sight of Jupiter and Saturn in the south after nightfall—and Jupiter is so bright, it comes out in the twilight, well before Saturn. On the 5th, the waxing moon hovers near Jupiter and almost directly above Antares, the brightest star in Scorpius. At 10:10 that night, Thursday, the 5th, the moon reaches first quarter phase. When the moon is at a quarter phase, the features of the lunar surface cast the deepest shadows, and this makes them stand out in sharpest relief. So this is a good night to explore the lighted part of the moon with binoculars. You don’t have to wait till after ten o’clock, of course; the moon is essentially at the first quarter phase all evening.

On the 7th, the moon will be bigger and brighter, this time closing in on Saturn. You may need binoculars to see it, but the star a few degrees below and right of the moon is the lid of the Teapot of Sagittarius. The Teapot will be somewhat washed out by moonlight, but if you haven’t seen it yet and would like to, that’s where to look for the lid, at least. On the 8th, the moon will be east of Saturn. On the 10th, the moon will be in the middle of the constellation Capricornus, the sea goat. Capricornus is chevron-shaped, and it’s one of the autumn water constellations. It has no bright stars, so it’s hard to find. But if you note where the moon is on the 10th and then find a star chart, that’ll vastly improve your chances of finding this dim constellation of the zodiac.

Three days later, on the 13th, we get a full moonrise. In Grand Marais, the moon rises at 7:36 p.m., four hours before it becomes perfectly full. Because it’s the closest full moon to the equinox, it qualifies as the harvest moon. The harvest moon got its name because near the time of the fall equinox, the moon can rise less than 30 minutes later from night to night as it goes from almost full to full to a couple of days past full, as opposed to forty or fifty minutes later from night to night near the solstices and more than an hour later from night to night near the spring equinox. The harvest moon gave extra moonlight to farmers working late to harvest their crops before they either froze or spoiled in the field. The harvest moon effect isn’t always as strong as the numbers I just gave would imply, but even so, this nickname for a full moon has a pretty solid basis.