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The Great Eclipse of 2017

On August 21st, 2017 the United States will be treated to an amazing astronomical event that many will go a lifetime without seeing...a total solar eclipse. Over a period of two minutes and forty seconds, the moon will completely block out the sun casting darkness over the earth below making the stars of the night sky visible in the middle of the day.

What is a Total Solar Eclipse?

A solar eclipse occurs during a new moon, when the moon travels between the Earth and the Sun blocking out the sun's rays casting a shadow on the earth below. From the perspective of those on the ground, the sky will turn to dusk and stars will become visible during the middle of the day.

There are three different types of solar eclipses, Partial, Annular and Total. There is also a rare hybrid eclipse that is combination of an Annular and Total Eclipse. 

Partial Eclipse 

  • A Partial Eclipse occurs when the Moon moves between the Earth and the Sun but they don't align perfectly. This leaves a portion of the sun visible as the Moon only covers a portion of the Sun's disk.  

Annular Eclipse

  • An eclipse that occurs when the Moon moves between the Earth and the Sun blocking out the center of the sun. However, during an Annular Eclipse the moon is further away from Earth making it impossible for the Moon to cover up the full disk of the Sun. This leaves a "ring of fire" or Annulus around the Moon.

Total Eclipse

  • A Total Eclipse occurs when the moon moves between the Earth and the Sun but blocks out the Sun entirely. When this happens, locations on Earth that fall within the darkest part of the Moon's shadow (Umbra) will experience complete darkness. 

This year's total eclipse will carve out a path of totality that will stretch from Oregon through portions of Missouri and Illinois all the way to South Carolina. The path of totality will move through southern Illinois from Millstadt to the Shawnee National Forest. Carbondale and the Shawnee National Forest will be great destinations to view the total eclipse. In southern Illinois, the Eclipse will begin around 11:52 AM and will end around 2:47 PM while totality is expected to last for about two minutes and forty seconds beginning around 1:20 PM and ending around 1:23 PM. 

Unfortunately, Central Illinois will not experience totality from this Solar Eclipse. Instead, we will get to experience a significant Partial Eclipse where coverage will range from 90% near Ottawa to 93% in the Peoria area to 96% near Springfield. For Peoria the eclipse will begin at 11:50 am with max coverage occurring at 1:17 pm. The eclipse and will end at 2:42 pm. 

What is the Safest Way to View the Eclipse?

Proper eyewear such as Eclipse Glasses or number 14 welder's glass will be needed to view the Eclipse while it's in its partial phase. This means you'll need to wear eye protection if you are planning on viewing the Solar Eclipse from here in Central Illinois where we will only be able to see a partial eclipse. For those viewing the eclipse in the path of totality, you'll need to wear eye protection for all phases of the eclipse except totality when the sun will be completely blocked out by the Moon. You can find eclipses glasses online or head over the Peoria Riverfront Museum where they have them on sale for less than $2.00. If you don't have a pair of certified solar glasses, you can make your own pinhole projector and view the eclipse without actually looking at the sun!

Why Don't Eclipses Occur Every Month? 

If the Moon's orbit around the earth was perfectly circular and in the same orbital plane as Earth we would experience a Solar Eclipse every month. Instead, the Moon's orbit is elliptical and its orbital plane is tilted more than 5° to the Earth's orbit around the Sun. This means that the distance between the Earth and the moon is constantly changing and since the Moon orbits on a tilted plane relative to Earth the Moon will often pass just above or just below the Sun's path in our sky. 

It's a misconception that Total Eclipses are a rare phenomenon but they are not common either. In fact, a Total Eclipse takes place somewhere on Earth approximately once every 18 months.

The last Total Solar Eclipse to occur in the contiguous United States was on February 26th, 1979 when the path of totality went through the northwestern states of Washington, Oregon, Idaho, Montana and North Dakota. If you are unable to watch this one, the next time you'll get to see a Total Eclipse in the contiguous United States will be on April 8th, 2024 where it will be visible from Texas to Maine. Oddly enough, the path of totality with this eclipse will also go through southern Illinois with totality lasting for more than four minutes!  It is estimated that total Solar Eclipses will recur for any given place on earth once every 360 to 410 years. So, experiencing two Total Eclipses in one location in a seven year period is exceptionally rare!

Typical Weather Conditions for Central and Southern Illinois During the Time of the Eclipse

It's far too soon to make an accurate weather forecast but we can look at what has happened in the past. According to the National Weather Service, temperatures are typically in the low to mid-80s with heat index values in the mid-80s during that part of the day. They say that the chance of clear to partly cloudy skies during this time of the eclipse is normally around 63%. 

See more information about this year's Solar Eclipse from the Peoria Riverfront Museum here. 

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