At the Farthest Edge of Sight
Saturday’s full moon, the closest to autumnal equinox, marks the famous Harvest Moon. Legend holds that farmers have long used the added light of this moon to continue bringing in the crops well into the night. Science backs up the legend.
This time of year, the moon travels a shallow, lazy arc along the ecliptic, midway between its highest transits in winter and its lowest path during summer. As a result, for us in mid-northern latitudes, moonrise changes by about 30 minutes for several nights either side of full, compared to almost an hour difference at other times of year. The farther north of the equator, the closer the time of moonrise. North of the Arctic Circle, the time of moonrise actually comes a few minutes earlier over the course of a few nights. Over that time, the moon rises in conjunction with sunset and sets with sunrise over several nights while also presenting a larger illuminated face to us.
Alas, all that moonlight will make it tough to take advantage of what is usually the best chance to see the most distant naked-eye planet. That same Saturday marks the opposition of Uranus, when it is directly opposite the sun from our earthbound vantage, thus appearing its brightest. At magnitude 5.7, distant Uranus is at the brink of what you can see with the unaided eye on a dark night.
A gas giant like the other outer planets, Uranus is surrounded by a dense atmosphere of ammonia and methane, giving it a blue-green color. The planet boasts 27 known moons and 13 rings, but unlike every other planet, Uranus stands on its side, its south pole facing the sun and its rings pointing up.
Saturday Uranus is four degrees below the full moon, so you’ll likely need binoculars or a modest telescope to spot it. Even then, at more than 1.6 billion miles from us, Uranus appears as a small, steady-glowing, blue-green speck.