Harvest Moon Quickly Dips Into Earth's Shadow – Sky & Telescope

I love it when an astronomical event occurs at a convenient time. Such will be the case when the Harvest Moon experiences a partial lunar eclipse on the night of September 17-18. Lucky observers in a good part of the Americas will be able to watch it without losing sleep. All or part of the lunar eclipse is visible from half the Earth. Observers in Europe and Africa will also enjoy views of the semi-obscured Moon, but during the first few hours after midnight.

As far as eclipses go, this one is minor, with a magnitude of just 0.09, meaning that the Earth's shadow will cover only 9% of the Moon's diameter at half the eclipse. In terms of total area, also called darkening3.8% of the Moon will remain in the umbra at most. Most of our satellite's time will be spent in the penumbra, or outer shadow cast by Earth; it spends only 65 minutes in the umbra. The shadow will appear to move from the northeast edge to the northwest edge as the Moon speeds eastward at about 3,960 kilometers per hour (2,460 mph). If that sounds fast, it is. The Moon reaches perigeeIts closest approach to Earth occurred around 9:30 a.m. EDT the following morning, traveling several hundred kilometers per hour faster than its average speed.

Eclipse phases by time zone

The proximity to perigee also means that the full Moon will appear larger than usual, swelling to an apparent diameter of 33.7′ or nearly 3′ larger than average. How cool! Without the extra circumference, the shadow's bite would be even smaller and the eclipse correspondingly shorter. The Harvest Moon will be the second closest full Moon of the year after October's Hunter's Moon. Since there's no way to directly compare a Moon at perigee to one at apogeeWhen the Moon is farthest from Earth, most people can't tell a difference in size. But if you take a quick photo with your smartphone and then do the same for the full Moon at apogee on April 13, 2025, you'll be able to tell them apart by placing the two unequal moons side by side.

You can observe the eclipse with your own eyes, binoculars, or a telescope. Most observers will detect the penumbral shading 30 to 40 minutes before the partial eclipse as a dull shadow along the eastern edge of the Moon (celestial east). As you move deeper into the penumbra, the shadow becomes more and more apparent, and the Moon looks like a dirty white plate.

I enjoy the soft, fuzzy appearance of the umbra's edge through the telescope as the primary eclipse begins. No matter which instrument is used, the gray veil of shadow will spread over the lunar north polar region like a gathering storm.

In case the weather gods alter your plans, you can watch the Harvest Moon eclipse online courtesy of Italian astronomer and astronomy popularizer Gianluca Masi. broadcast the show live The total lunar eclipse will begin at 00:30 UT on September 18 (8:30 p.m. EDT on September 17). The next total lunar eclipse will occur on March 13-14, 2025, and will be centered over the Americas.

More lunar fun

On September 17, the morning before the eclipse, observers in the western half of North America, Hawaii, and parts of Indonesia and Australia will be able to see the crescent Moon occult the planet Saturn. International Occultation Timing Association website Five mornings later, on Sept. 22, the waning gibbous Moon will occult the Pleiades star cluster. The passage is near central to many locations in the United States, and multiple stars will be obscured. Observers in the eastern half of the country will see the occultation during morning twilight; in the western states, it will occur in the dark.

To determine the Moon's path through the cluster and to find out which stars will disappear and reappear at your location, simulate the occultation using a free software application such as Stellarium Mobile. After downloading it from Google Play or Apple App StoreSet the date and play with time. As you move the clock forward, watch the times the Moon covers and discovers various members of the cluster. You can also download Stellarium for your laptop or just use the interactive web version, Stellarium WebsiteIt couldn't be easier. Enjoy your moments with the Moon this month.