The Moon of the Autumn Equinox
The Harvest Moon is usually defined as the full moon closest to the autumn equinox. For us in the Northern Hemisphere, that usually occurs on or near September 22 each year. This year however, the nearest full moon to the equinox will occur this week on October 5, 2017.
Many people think this full moon gets its name from a reddish glow that may appear on the full moon. But that red color doesn’t happen with every Fall Full Moon. This effect is caused by the atmosphere of the earth. When sunlight is scattered by passing through Earth’s atmosphere, the other colors of the spectrum are removed. The moon will appear reddish when it’s nearer to the horizon, for the same reason a sunset or sunrise appears red. It’s all because of the Earth’s shadow.
A red moon is sometimes used to refer to four total lunar eclipses that happen in the space of two years, a phenomenon astronomers call a lunar tetrad. The eclipses in a tetrad occur six months apart with at least six Full Moons between them. So a red moon, isn’t a completely rare thing when an eclipse occurs.
A lot of Space or Astronomical journals have begun using the term “Blood Moon” to describe all these red moon occurrences. Unfortunately they didn’t do their research and made some significant assumptions about the phrase. It has nothing to do with the color of the moon at all. Continue reading