We had thunderstorms move through the area yesterday evening. As often happens during summer showers, the sun peeked out at the end, and shot light across the rain still falling at my house, producing a spectacular rainbow. The rainbow was fainter than most because the sun was nearly level with the western horizon and already deeply reddened. To my amazement parts of the bow were still visible as late as 9:05 p.m. — a full 5 minutes after sundown.
Perhaps you live where thunderstorms are common in the summer months. Today we’ll use them to introduce the Thunder Moon, one of the traditional names for July’s full moon. Watch for it to rise in the southeastern sky in Sagittarius Tuesday night (July 16) right around the time of sunset. To pinpoint the time of moonrise for your location use this handy calculator. Full moons are always fun to watch. I look forward to their rising each month and try to figure out new ways to photograph them.
Watching a moonrise in binoculars or a small telescope reveals much about the otherwise invisible air layers in the lower atmosphere. Turbulence will make the magnified image flutter and ripple especially when viewed near the horizon. If you’re lucky, the air will be stratified in layers according to temperature and pressure and temperature like a nice, flaky baklava. As the rising moon pushes through them you can watch individual “steps” appear and disappear along the lunar circumference.
Observers in India, Africa, Europe and much of South America will witness a partial lunar eclipse Tuesday night. The eclipse will be over by the time the moon rises for observers in North America. Too bad. But like the solar eclipse earlier this month, you can still see it via live feed. Italian astrophysicist Gianluca Masi will offer a live stream Tuesday starting at 3:30 p.m. CDT (20:30 UT) with a view of the chomped moon climbing over a Roman skyline.
65 percent of the moon will soak in Earth’s shadow at maximum so skywatchers should definitely be able to see the red color of the moon’s darkened half. As well, the sky will darken enough to see the brighter parts of the Milky Way. Even though this is only a partial eclipse, it’s special because it happens exactly 50 years to the day the Apollo 11 mission blasted off for the moon.
Before you get excited about the Thunder Moon, take a look at tonight’s 99.5-percent-full moon (July 15). It will be in close conjunction with the planet Saturn, shining just a degree away. The duo will be closest around 3 a.m. CDT Tuesday morning with a separation of just ¾°. Fun!