Supermoon Eclipse is Sunday

Sep 25, 2015

Credit NASA

Fall is right around the corner and if you’re a stargazer this is good news.  The nights are longer, the temperatures cooler and the bugs will soon be gone. This month is a great time to get out and observe one of nature’s best events - a total lunar eclipse.  

It happens when the full moon passes through the darkest part of earth’s shadow, called the umbra. You don’t see a lunar eclipse every month because the moon’s orbit is tilted about 5 degrees to the plane of earth’s orbit around the sun.  But once or twice a year, the moon, earth and sun line up just right, and an eclipse occurs.

This month’s eclipse is the last of a lunar tetrad.  That means there are four total lunar eclipses in a row.  Each eclipse is separated by 6 months with no partial eclipses in between.  This lunar tetrad began in April 2014, with another eclipse in October, and another in April of 2015.  And this month’s eclipse on the 27th may be the best of them all.  

Here’s why.  Nearly all of this month’s eclipse will be visible to Kansas and the eastern United States.  Sometimes, the moon is rising or setting while eclipsed and we only get to see part of it.   Also this month’s eclipse happens in the evening right after sunset. That means you won’t have to crawl out of bed at 3 in the morning to see it.  And last but not least, this month’s eçlipse is no ordinary moon - it’s a Supermoon!

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During a Supermoon, the full moon appears bigger and brighter than usual.  This happens because the moon’s distance from earth varies.  The moon’s orbit is not a circle; it’s an ellipse.  Its average distance is 239,000 miles. But it can be as far away as 252,000 miles, called apogee, and as close as 226,000 miles, called perigee.  This month’s eclipse happens when the moon is at perigee, making it a Supermoon.  The moon will appear 14 percent larger and 30 percent brighter than the full moon at apogee.  That is until it is darkened by the eclipse anyway.

If you’d like to view this month’s eclipse, go out on Sunday, Sept 27 shortly after 8 pm and look for the full moon low in the east.  About this time, Earth’s shadow begins creeping up the eastern limb of the moon.  By about 9 pm, the moon will be completely covered by Earth’s shadow.  The shadow begins to recede by 10:30 pm.  And around 11:30 pm the moon emerges from the shadow making the whole thing last over 3 hours.  So basically if you go out and look at the moon anytime between 8 pm to 11:30 pm you will see the moon in some stage of the eclipse. You don’t need special equipment to observe a lunar eclipse, but binoculars will enhance the viewing experience.