Moon Illusion to Supersize Saturday Lunar Eclipse

Moon Illusion to Supersize Saturday Lunar Eclipse
The moon's path through Earth's shadow on June 26th, when a partial lunar eclipse will be visible over North America and other parts of the world. The eclipse should appear more spectacular because of an optical illusion. Full Story Image (Image credit: F. Espenak/GSFC)

A partial lunar eclipse set to occur early Saturday shouldlook particularly stunning to observers in parts of North America thanks to anoptical illusion that will make the moon look bigger than normal.

The moon will pass through part of Earth's shadow,temporarily becoming dark, starting at 6:17 a.m. EDT (1017 GMT) Saturdaymorning. That cosmic line-up coincides with the fullmoon of June and a so-called "moon illusion" that, weatherpermitting, should offer quite a show, according to a NASA announcement.

For observers in the central and western United States, the lunareclipse will occur while the moon is still close to the horizon. Thepartial eclipse begins after the moon has set for observers in the easternUnited States. (This graphic shows how the moon will appear during Saturday'sthree-hour partial lunar eclipse.)?

Even though only 54 percent of the moon's diameter will becovered during the moment of greatest eclipse (around 7:38 a.m. EDT, 1138 GMT),the sight will appear magnified in size and charm by the "moonillusion." [Top10 lunar eclipse facts]

Scientists aren't completely sure why, but low-hangingmoons tend to look exceptionally large. When the moon beams through trees,buildings and other foreground objects close to the horizon, it often appearsto be much larger than when it shines from overhead.

Even though cameras prove that low moons are no wider thanany other moons, the human brain insists otherwise.

The moon will be most picturesque in the western and centralparts of the United States where the moon will be setting as the eclipsereaches maximum. Viewers there should look low and to the west just before dawnto catch the best sight.

The same phenomenon will be visible to observers in India,Japan, and parts of East Asia. The eclipse will occur there on Saturday eveningas the moon is rising, with the same illusion in full force. However, in theislands of the South Pacific, the moon will be hanging directly overhead in themidnight sky, so the horizon illusion won't add to the effect.

People in New England and northeastern Canada will just missbeing able to see the eclipse.

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