Skywatch Line for Friday, August 30 through Sunday, September 1, 2019

This is Dudley Observatory’s Skywatch Line for Friday, August 30 through Sunday, September 1, written by Sam Salem.

On Friday, Sun rises at 6:18am and sets at 7:34pm; the new Moon rises at 6:14am and sets at 8:09pm. Friday presents the closest new Moon supermoon of the year. The Moon will be at 221,971 miles distance from Earth. This is the year’s closest coincidence of new Moon with lunar perigee, the Moon’s nearest point to Earth in its monthly orbit. On Friday, the new Moon occurs at 6:37am, Perigee occurs at 1:57pm. The tidal influence of the extra-close new Moon and the Sun team up to usher in extra large spring tides. The ecliptic hits the sunset horizon at a shallow angle in late summer, tending to bury the young Moon in the glare of evening twilight. Fortunately, this particular young Moon swings a maximum of 5 degrees, about 10 moon-diameters, north of the ecliptic. This gives people in Northern Hemisphere a better opportunity for catching a late-summer young Moon. You will have a better chance watching the young Moon on Saturday and Sunday. The young waxing crescent will be about 4 percent illuminated at sunset on Saturday. Spica, the constellation Virgo’s one and only 1st-magnitude star, is the bright star close to the young Moon on Sunday.

The westward advance of stars and planets is mostly cancelled out by progressively earlier nightfall. This extends the opportunity for watching Jupiter and Saturn. Jupiter at magnitude -2.2 is an easy twilight target. You should be able to pick out Jupiter, low in the south, fifteen minutes after sunset. Jupiter sets a few minutes before midnight. Saturn, at magnitude 0.3, in constellation Sagittarius is located 30 degrees left or upper left of Jupiter. Its location farther east is slightly more favorable for telescopic observers. The ringed planet doesn’t culminate until around 9:30pm. Saturn sets around 2am. If you’re fortunate enough to catch some steady seeing conditions, both planets can display fascinating detail in relatively modest telescopes.

Uranus, at magnitude 5.8, in constellation Aries, lies high in the south just before the beginning of dawn. Neptune, at magnitude 7.8, in constellation Aquarius, is well up in the southeast by 11pm. and highest in the south by 2am.

Moonlight-free nights over this weekend offer a good opportunity for some deep-sky observing. Early evening is the ideal time to enjoy the swarm of globular clusters that congregate in and around the southern Milky Way. Constellations Sagittarius and Ophiuchus harbor seven globulars each, nearly half the total in the entire Messier catalogue. Of the 14 globular clusters scattered across this region, M22 is the best in constellation Sagittarius. This superb cluster is a delight in any telescope. However, the more aperture you can bring to bear, the more individual stars you’ll see. You can easily spot M22 in 10×50 binoculars. It’s big enough to be conspicuously non-stellar even at such low magnification. Glowing at magnitude 5.1, M22 happens to be the brightest Messier globular. Using binoculars, or a finder scope, you’ll find M22 about 2½ degrees northeast of 2.8-magnitude Lambda (λ) Sagittarii, the star marking the top of the Sagittarius Teapot. Use planet Saturn to guide you to constellation Sagittarius. The handle of the Sagittarius Teapot lies below Saturn. You can catch a second globular, M28, in the same binocular field one degree northwest of Lambda. At magnitude 6.8 and only half the size of M22, M28 is not nearly as impressive as M22.

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