Mon Jul 27, 2026 THOMAS HARRIOT BEATS GALILEO
Toward the end of July in the year 1609, the Englishman Thomas Harriot made the first detailed drawings of the moon as seen through a telescope. Galileo would make his drawings several months later, not quite as good as Harriot’s, but while Galileo became famous, hardly anyone has ever heard of Harriot. Galileo published his discoveries in a widely read book, The Starry Messenger. Harriot wrote manuscripts, but never published a book for public consumption. Harriot led an interesting life, accompanying Sir Walter Raleigh to the Roanoke colony in America, serving as mathematician, navigator and interpreter. He was briefly imprisoned in 1605 on account of suspicions that he had been part of the assassination attempt on King James 1. He was innocent and released, but this may have made him less eager to publish, not wishing to draw attention to himself.
Tue Jul 28, 2026 FULL MOON HANGS LOW
All full moons rise at sunset and set at sunrise. So full moons are at their highest around the midnight hour (or 1 am, if you throw in daylight savings time.) But even though it’s at its highest then, July’s full moon isn’t very high. You see, full moons are directly opposite the sun. So they occupy the part of the sky where the sun will be found six months later. Half a year from now it will be winter, and the sun’s path in winter is very low; even at noon it’s not far off the south horizon. In summer the full moon is at the spot where the sun would be in winter. So the summer’s full moon mimics the sun’s wintertime path. This also means that full moons in winter can reach the top of the sky at midnight, mimicking the sun’s path in summertime. But this month’s full moon won’t get very far above the horizon, and will be at a convenient altitude for us to admire it, just above the treetops, low in the southern sky at the midnight hour. Check out the full moon these next few nights.
Wed Jul 29, 2026 JULY FULL MOON
The moon is full tonight. Because thunderstorms are common in July, this full moon is often called the Thunder moon. According to the Sioux Indians, this is the Moon When the Wild Cherries Are Ripe. To the Winnebago, it is the Corn-Ripening Moon, and to the Kiowas, it is the Moon of Deer Horns Dropping Off. To the Omaha Indians, however, this is the Moon When the Buffalo Bellow. In ancient China, this was the Hungry Ghost Moon, named for departed souls who had left no descendants. In medieval times this was the Hay Moon or the Mead Moon, named for the elixir from the meadows of Briton and Europe. After this full moon came the first harvests from the fields and the pagan festival of Lughnasaid, which was later adopted by early Christians and became the celebration of Lammas, or “loaf mass,” in thanksgiving for the first fruits of the farmer’s labor.
Thu Jul 30, 2026 GALILEO SEES SATURN
On July 30th 1610 Galileo set up a small, hand-made telescope on his veranda in Padua, and aimed it at a bright yellow, star-like object in the night sky. So what did he see? Just a small round blob of light, and on either side, two even smaller blobs. Were these two large moons of Saturn? Did the planet have handles? Or ears? He couldn’t tell. His crude telescope only magnified objects about 30 times, which wasn’t enough to resolve the mysterious somethings that flanked the sixth planet. Galileo recorded what he saw, then moved on to other discoveries. It wasn’t until 1655 that better telescopes resolved those blobs into rings. Now, 400 years later, even small telescopes are good enough to resolve the rings of Saturn; after midnight you can find the ringed planet low in the eastern sky in the constellation Pisces.
Fri Jul 31, 2026 THE MAYAN CALENDAR
Today’s Skywatch was written by my student assistant, Isabella Gargiulo. The Maya, an ancient Mesoamerican civilization, based many aspects of their daily lives on the movements of planets, outlines of constellations, and the path of our Sun through the sky. Using only their naked eye and simple measuring devices, the Maya were able to predict the times of eclipses, as well as where Mars and Venus could be found in the sky. Their observations were recorded in a book called the Dresden Codex. The planet Venus, which can be seen in the western evening sky this time of year, was the most significant celestial body to the Maya. They used Venus’s orbital period to mark times for planting crops and harvesting or when to go to war. They were able to measure Venus’s synodic period, the time it takes the planet to go from between the Earth and Sun and back again, to 583.92 days. They happened to be off by just 14 minutes.
