Jimmy Westlake: Total eclipse to darken the moon Sunday
September 21, 2015
A week out from next Sunday's total lunar eclipse, the weather forecast for Northwest Colorado is looking pretty good. The student members of the Colorado Mountain College SKY Club and I, along with Steamboat Today, would like to invite you and your family out to the CMC campus next Sunday evening for a special "Eclipse Watch" program.
Join us in the Allbright Family Auditorium at 6:30 p.m. for my "Shadows in Space" program, when I will explain all about solar and lunar eclipses. Afterward, we will adjourn to the deck and patio outside the auditorium to watch the moon slip into the shadow of the Earth. Telescopes will be set up for close-up viewing, however, no optical aid is required to watch and enjoy this beautiful event.
Sunday's total lunar eclipse will be the fourth and final eclipse in the current tetrad we've been enjoying for the past two years. It's easy to become jaded to these unusual events when they happen every six months, but remember — seeing four consecutive total lunar eclipses from the same location on Earth is exceedingly rare.
You have to go back to the years 1967-68 for a previous tetrad of total lunar eclipses visible from Colorado, and it won't happen again in this century. Typically, total lunar eclipses can be seen from any given location about once every three years on average, so, four eclipses in two years is quite phenomenal.
Earth, sun and moon are in the proper alignment for eclipses to happen during two brief windows called "eclipse seasons," about six months apart.
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Sunday's eclipse happens during prime time, finishing up before bedtime for most folks in Colorado. And, to make it even more special, this eclipse happens when the full Harvest Moon is at perigee — its closest point to Earth. That means it will be a super full moon, 7 percent larger than your average full moon and the largest of 2015.
You might notice a slight shading on the lower edge of the full Harvest Moon when it rises at 6:51 p.m. Sunday night. The partial phase of the eclipse officially begins minutes later, at 7:12 p.m.
For the next hour, the Super Harvest Moon will mover deeper and deeper into the Earth's shadow until, at 8:13 pm, totality begins and the moon will turn a deep shade of orange and red. Mid-eclipse occurs at 8:47 p.m. and totality ends at 9:22 p.m. It will take until 10:23 p.m. for the moon to completely emerge back into the sunshine and then, the eclipse will be over.
The moon glows with an eerie red color during a total lunar eclipse because the Earth's atmosphere strips the sunlight of all of its blue and violet colors before bending it into the shadow to illuminate the moon. Put a different way, the red light that illuminates the moon during a lunar eclipse is the combined light of every sunrise and sunset on Earth at that moment, projected onto the moon.
If you were standing on the moon during a total lunar eclipse and looking up at the Earth in your sky, the Earth would be covering up the sun but sunlight passing through Earth's atmosphere would create a brightly glowing, reddish-orange ring around the Earth. No two eclipse colors are ever quite the same because clouds and dust in Earth's atmosphere are always changing.
So, I hope that you will spend your Sunday evening with me, the CMC SKY Club and the Steamboat Today as we learn about eclipses and watch the spectacular total eclipse of the Super Harvest Moon.
If you miss this one, you'll have to wait until Jan. 31, 2018, for the next total lunar eclipse visible from Colorado.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Westlakes's astrophotography website at http://www.jwestlake.com.