Super moon, harvest moon, eclipse converge

On Sunday we will truly have a rare event in the Butler sky, something that we haven’t had for at least a hundred years and something we won’t have again for least another hundred years.

We have three for the price on one Sunday; a harvest moon, a super moon, and total lunar eclipse. Do whatever you can to see this, even if you have to drive a little bit to where the skies are clear. It’s that rare of an event.

Harvest moons in and of themselves are certainly not rare. They occur every year. Astronomically, it’s the monthly full moon closest to the date of autumnal equinox, which was last Wednesday.

Because of where the full moon is among the background stars this time of year, it rises only about 20 minutes later each night. It normally rises about 30 to 60 minutes later from night to night.

We don’t have an outright extension of daylight this week, but the full moon keeps the total darkness away for a while, at least in the countryside away from light polluted plagued areas.

Super moons also in and of themselves are certainly not rare. We also have them every year, and last year we had one at harvest moon time.

I have to admit — and I don’t mean to be a buzzkill — but that term has never sat well with me.

It’s become a media darling that has more to do with astrology and pop cultural than astronomy. It’s based on the astronomical term, perigee full moon.

Because of the oblong shape of the moon’s orbit around the Earth, every month it achieves its maximum distance to the Earth apogee, at a little more than 250,000 miles. The closest distance, called perigee, is a little more than 225,000 miles.

The perigee full moon is actually next month, but it’s close to being one Sunday so it meets the super moon criteria.

There’s no doubt the full moon is bigger in the sky during a super moon, but it’s only about 7 percent larger than the average full moon and about 14 percent brighter.

I really doubt anyone, including myself, can really tell the difference in size between an average full moon and a super moon. Again — not to be a buzzkill — but the power of suggestion can be very powerful.

On the main menu is the total lunar eclipse. It’s the fourth one we’ve had in two years and the last one we’ll see around here until 2019.

It’ll be a prime-time event. The eclipse starts at 9:07 p.m. when the full moon starts to slip into the Earth’s ruddy shadow. The moon will be totally eclipsed from 10:11 p.m. to 11:23 p.m.

You don’t need any special equipment to see the lunar eclipse as you do for solar eclipses.

It’s perfectly safe to stare at for as long as you want with your naked eyes. But remember that staring at any full moon can bring about a little madness in some people.

Seriously though, lunar eclipses are wonderful events to witness and this one offers you a unique way to end your day.

A lunar eclipse is also a lot more frequent than a solar eclipse and can be seen anywhere in the world where the full moon is visible during the time of the eclipse.

As you can see in the diagram, lunar eclipses occur when the moon in its monthly orbit around our world passes through the shadow of the Earth in the opposite direction from the sun.

This can only happen during full moons, but doesn’t happen every time there’s a full moon because the moon’s orbit around the Earth is inclined by five degrees to the Earth’s orbit around the sun. Most months the full moon misses the 6,000-mile wide shadow, known as the umbra.

The moon doesn’t totally black out during lunar eclipses because the umbra shadow is not totally dark. Strained sunlight finds its way to the moon through the shell of atmosphere that covers our Earth.

Most of the blue and yellow components of the sun’s light is scattered by Earth’s atmosphere leaving only a reddish glow sent in the direction of the moon.

This same effect causes orange reddish sunrises and sunsets and has the same effect on moonrises and moonsets.

Another pop culture term that’s emerged in the last couple of years is to refer to a totally eclipsed moon as a blood moon just because of its bloody red color and nothing else. It’s not based of anything technical or astronomical, and it certainly doesn’t suggest that you should be afraid of lunar eclipses.

So enjoy the trifecta Sunday of the full harvest moon, the super moon and the last total lunar eclipse until January of 2019.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/Paul and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications and available at bookstores and at www.adventurepublications.net.