When the sun sets this evening in the Northern hemisphere, look to the horizon for a special celestial treat—the harvest moon.
The harvest moon is the name given to the full moon that occurs closest to the autumn equinox, which happens on Sept. 23 this year. In most years, the harvest moon takes place in September, but one-third of instances occur in October.
The annual spectacle is unique because for several evenings around the event, the moon rises from the east within 30 minutes after sunset, in contrast to other full moons which arise about 50 minutes after the sun disappears.
Historically, this shorter delay between sunset and moonrise has allowed farmers more light by which to harvest their autumn crops.
For the past few days, as it has been moving towards its peak fullness, the moon has appeared to hang low in the southeastern sky.
Due to the relative proximity to the horizon, the harvest moon seems bigger and brighter, with many of its detailed features observable using simple binoculars and telescopes.
Since ancient times, Chinese people have been able to calculate the date of the harvest moon each day, celebrating it as the Mid-Autumn Festival.
The exact time of the full moon is 5:27 a.m. EDT on Sept. 12.
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