Harvest Moon Eclipse

This year, it seems, summer will leave us with a big light show in the evening sky.

Sunday, Sept. 22, officially marks the end of summer and the beginning of autumn. The autumnal equinox, as it's called, is that moment in space-time when the sun's most direct rays are shining right on the equator, equally distant from the North and South poles.

Here in the middle latitudes, not very far north or south, we experience nearly equal amounts of daylight and darkness -- 12 hours to a side.

Equinoxes were special moments for our ancestors. Calendars were created around them; crops were planted by them. The Harvest Moon, one of the most important Full Moons of the year, was identified as the first Full Moon following the autumnal equinox.

This year the moment of the autumnal equinox, marked by the Sun's entrance into the constellation Libra, occurs at 11:00 a.m. Pacific Daylight Time on Sept. 22. The Harvest Moon, or the first Full Moon after that date, will occur on Friday, Sept. 27.

But on Thursday evening, just as the Harvest Moon is nearing its maximum size, a spectacular event will occur that won't be repeated for nearly 20 years.

At about 7:40 p.m. Pacific Daylight Time, the Harvest Moon will be rising above the eastern horizon. Where harvest dust and smoke from summer wildfires linger in the air, it will glow a brilliant red-orange. And, barring cloudy skies or other obstructions to the east, its full orb will clear the horizon just as it begins to lose face.

Within a few moments it will look like someone with large jaws has taken a bite out of the Harvest Moon and the darkness in that wound will spread, irresistably, until the entire moon, once so bright and colorful, is consumed.

Left behind, and glowing ever more brightly near the space where the moon disappears, will be the planet Saturn.

The total eclipse of the Harvest Moon only lasts a few minutes and won't be repeated in these parts until 2015. Take a moment to watch this one.

"Because we don't know when we will die we get to think of life as an inexhaustible well," wrote Paul Bowles in The Sheltering Sky. "Yet everything happens only a certain number of times, and a very small number really... How many more times will you watch the full moon rise, perhaps twenty and yet it all seems limitless."