Total Lunar Eclipse – January 31, 2018

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On Wednesday, January 31, 2018, all of the USA will be able to enjoy a total lunar eclipse. This is the first eclipse to happen during a Blue Moon –the second full moon within a calendar month– since 1866. A similar phenomenon will happen again until 2028.

A lunar eclipse occurs when the Moon passes directly behind the Earth into its shadow. There are two types of shadows: the penumbra is a lighter shadow, while the umbra is darker. During a total lunar eclipse the moon passes through both shadows; when the moon’s full disc is inside the umbra, we call it totality.

The Moon’s appearance during a total lunar eclipse can vary enormously from one eclipse to the next. Although the Earth blocks off all direct sunlight from the umbra, the planet’s atmosphere redirects some of the Sun’s rays into the shadow. Elements in Earth’s atmosphere affect the final color during totality; look at the eclipse during the maximum and assign a value within the Danjon scale. There is no way to precisely predict the color the Moon will take during the eclipse.


Riverside, CA will be able to see the full eclipse when in totality, but the moon will set before it exits the penumbra.

  • 2:51 AM (PST) – Beginning of penumbral eclipse
  • 3:48 AM – Beginning of umbral eclipse
  • 4:51 AM – Beginning of totality
  • 5:31 AM – Maximum eclipse (the moon is deepest in the umbra)
  • 6:07 AM – End of totality
  • 6:56 AM – Moon sets behind horizon
  • 7:11 AM – End of umbral eclipse (not visible from Riverside)
  • 8:08 AM – End of penumbral eclipse (not visible from Riverside)

UC Riverside will not hold a public observation due to the time of day. We will host an event for the next total lunar eclipse on January 21, 2019, mark your calendars!

Model of the moon’s position as seen from Riverside, relative to the western horizon. Each horizontal line, starting from the horizon, represents 5 degrees. The eclipse starts at 2:51 AM with the moon around 40 degrees above the western horizon.


Lunar eclipses are perfectly safe to view with the unaided eye. You can improve your experience by looking through binoculars or a telescope.



  • Total lunar eclipse photograph from Florida in 2015 by Rhona Wise / EPA
  • Model of the moon position generated with Stellarium
  • Danjon scale illustrated by Mario De Leo-Winkler