Autumn Equinox

We’ve been getting a lot of rain which is good, but hopefully the sky will have cleared, and we can welcome the Harvest Moon!

The full moon closest to the autumn equinox is known as the Harvest Moon. This year the Harvest Moon is on the 19th, followed by the autumn equinox on the 22nd. Don’t forget that the Orionid meteor shower peaks on the 21st, but it lasts a long time. It started on Oct. 2 and lasts until Nov. 7.

So why is the Harvest Moon so special? Like any full moon it rises at sunset and sets at sunrise. On average, the moon rises about an hour later each night, but the Harvest Moon rises only 30 minutes later for several evenings in a row. This is because in the fall, the ecliptic that the Sun and Moon travel along is closer to the horizon at night, resulting in a shorter time between moon rises. This longer bright light helped farmers harvest their crops. Hence the name Harvest Moon!

Because the Moon is so low in the sky, it appears larger and brighter than normal. This is merely an optical illusion. Also, being so low causes its reflected sunlight to pass through more of Earth’s atmosphere, making the light redder. The atmospheric particles scatter the bluish component of light, which is why the sky appears blue. They allow the reddish light to travel straight to our eyes, so any light low on the horizon appears red.

So, when the Sun is close to the spring and fall equinox, it sets faster than it does near the summer and winter solstice. This is because the Sun sets due west and hits the horizon at the steepest possible angle.

On the solstice, the Sun is either its farthest north or south and sets at a shallower angle, which takes longer.  This also applies to sunrise. The solstice is either the longest or shortest day of the year, depending on whether it occurs in June or December.

Equinox is when the Sun crosses the equator, and either moves above or below it is heading toward summer or winter.

Mars, Jupiter and Saturn are October’s major attractions. Saturn is east and is visible at nightfall. It doesn’t set until 3 a.m. in early October, and shortly before 1 a.m. by the end of the month. Jupiter is the brightest object in the sky aside from the bright Moon. It’s visible all evening. It dims slightly by the end of the month. Jupiter is also in the east. Mars isn’t visible until midnight.  The Moon joins Mars on the 14th. Mercury rises in the east 60 minutes before sunrise. Venus is now out of view.


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