Globe at Night - How Dark Does the Sky Get During a Solar Eclipse?

Map of the path of totality of the 2017 Total Solar Eclipse

“On August 21, 2017, millions of people across the United States will see nature's most wondrous spectacle — a total eclipse of the Sun. It is a scene of unimaginable beauty; the Moon completely blocks the Sun, daytime becomes a deep twilight, and the Sun’s corona shimmers in the darkened sky.” For more information on the total solar eclipse (e.g., locations for the eclipse path and the local times for totality), visit

If you are on or near the centerline of the path of totality during the solar eclipse on August 21, 2017, you are able to participate in an activity to observe and record the faintest stars visible as a means of measuring how dark the daytime sky gets. By locating and observing the constellation Ursa Major (e.g, the Big Dipper) midway during the solar eclipse and comparing it to stellar charts, your “measurement” and submission of that measurement to the online database will document darkness levels of a daytime sky during a total solar eclipse. Your measurement will help scientific research.