The harvest moon is giant and red upon the horizon because it rises at sunset.

That Big Pumpkin in the Sky: Harvest Moon Really Shines This Week


The harvest moon is still upon us, as the fall equinox approaches this weekend.

The fullest moon of the month fell on the night of September 18-19, but as NASA points out in this video, the moon is in the midst of a string of days during which it rises at sunset. And when that happens, the horizon-moon illusion combines with the sunset colors to redden it.

“When you add these effects together the Harvest Moon often looks like a great pumpkin,” NASA says. “The experience is repeated for several nights in a row around the equinox.”

So check the horizon tonight for a giant pumpkin. The fall equinox arrives on Sunday September 22.

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