Lunar Eclipse Set For September 27

Sep 18, 2015

By Dave Cuomo, Willard Smith Planetarium Supervisor

Lunar Eclipse Diagram


On the evening of Sunday, September 27, 2015 Seattle residents will be able to witness the Earth’s shadow pass over the Moon causing a total eclipse. The eclipse begins at 5:11 p.m. so it will already be in progress when the Moon rises at 6:55 p.m. When the Moon rises, Seattleites will be able to see the curvature of the Earth’s shadow across the face of the Moon. The Ancient Greeks witnessed this and, using simple geography along with their knowledge of the circumference of the Earth, were able to estimate the distance between the Earth and the Moon at 240,000 miles, remarkably close to our current calculation of the average distance at 238,000 miles. Over the next 52 minutes you will be able to see the shadow of the Earth slowly cover the Moon until it is totally eclipsed at 7:47 p.m. The Earth’s shadow will then slowly recede and the eclipse will be over by 9:27 p.m.

During the eclipse the Moon may appear blood red. While in the past this was seen as ominous we know it is because of the Earth’s atmosphere. The light from the Sun passes through the edges of the atmosphere. By passing through the atmosphere the blue light is scattered and the red light makes it through reflecting off of the Moon back to us. This is the same effect that we witness at sunset and sunrise.

To best view the eclipse, find an area with an unobstructed view to the East. While a dark sky location is ideal it is not a necessity to enjoy the eclipse.