The very longest duration of eclipse is in southern Illinois.
Total solar eclipse over Illinois
The Land of Lincoln will enjoy its moment under the eclipsed Sun.
Only the southernmost section of Illinois enjoys totality, but this state has bragging rights for the longest duration of the total solar eclipse along the entire path if only by a tiny whisker over Kentucky.
Eclipse calculations today are extremely precise. Not only are the best ephemerides for the motions of the solar system bodies used, but precise topographic models of the Moon are employed to discern which lunar valley or low point will pierce the Sun's disk early or late to affect the precise duration of eclipse. These calculations point to the very longest duration to be at 37.568 degrees North latitude and 89.1029 degrees West longitude. Near this spot is a name that warms the heart of eclipse chasers: Blue Skies Vineyard.
If you wish to find the spot of longest eclipse, visit this Google interactive map by Xavier Jubier and look for the green pin near Carbondale: http://xjubier.free.fr/en/site_pages/solar_eclipses/TSE_2017_GoogleMapFull.html
The bigger question is: how important is point of longest duration? Truth be told, not very. It's a fun fact but the three overwhelming considerations for a viewing location on eclipse day are weather, weather, and weather. If the short-term weather forecast here is good, enjoy a glass of vino at the vineyard under the shadow of the Moon. If not, drive to where there are blue skies, hundreds of miles if necessary.
Carbondale gets 2 minutes and 35 seconds of totality. Marion has 2 minutes and 28 seconds. The total solar eclipse enters Illinois at 1:17 p.m. CDT and leaves at 1:25 p.m. The shadow of the Moon is speeding through Illinois at about 1825 miles per hour!
Click to buy 11" by 17" detailed eclipse map of illinois
CLICK FOR THE Illinois STATE PAGE ON ECLIPSEWISE.COM. THE SITE PROVIDES THE MOST COMPREHENSIVE AND AUTHORITATIVE STATE PAGES FOR THE 2017 ECLIPSE. ECLIPSEWISE.COM IS BUILT BY FRED ESPENAK, RETIRED NASA ASTROPHYSICIST AND THE LEADING EXPERT ON ECLIPSE PREDICTIONS.
Illinois will be a popular destination for many people and we estimate that the centerline in Illinois is the closest destination for for 26 million Americans. We further estimate that between 93,000 and 372,000 will travel to the centerline in southern Illinois on eclipse day. Details at www.greatamericaneclipse.com/statistics/
Eclipse viewing activities in the Carbondale area are being coordinated by Southern Illinois University. Visit http://eclipse.siu.edu/ for details.
Dan McGlaun of eclipse2017.org has a great page dedicated to detailed eclipse predictions for communities within the path of totality in Illinois at http://www.eclipse2017.org/2017/states/IL.htm
