Beautiful blue sky morning. I walked the dog, noted the light coating of frost on the lawn and looked up to see a crisp last quarter moon riding over the poplar tops. Only a few yellow-brown leaves wagged way up there, but the contrasts of sky, moon and autumnal color made for a refreshing way to start the day.
After full moon, we often lose track of the moon’s doing because it rises later and later at night. Up until full moon, it’s always up in the afternoon or early evening sky, making it hard to miss. Each day (or night), the moon moves about a fist to the east or left as seen in the northern hemisphere. The full moon rises at sunset, the day after full about an hour later, and the day after that another hour later. By the time of last quarter phase or seven days past full, the moon rises around midnight, a time when many of us are in bed.
By sunrise, the last quarter stands straight up due south at its maximum altitude. And since the sun rises so late in late October (after 7:30 a.m. from many locations), it’s easy to spot the last quarter moon high in the southwestern sky anytime from sunrise till 11 in the morning.
Late-rising moons are great times for aurora watching because the sky remains dark for much of the night. This weekend, space weather experts predict minor G1 geomagnetic storms. We might see a low arc or two in the northern sky early this evening (Oct. 22) with better chances for a more extended and active aurora Sunday night Oct. 23. Solar coronal holes and a glancing blow from a CME or coronal mass ejection are treat-or-treating our planet with a bounty of electrons and protons.