Earth Shadow Setting Sequence
November 17, 2008
The photo sequence above shows the setting of the Earth's shadow as observed from eastern Kansas. Though the rising of the Earth's shadow above the eastern horizon is commonly seen ( Belt of Venus) it's much more difficult to notice the shadow as it approaches the western horizon. Since mid August I had been observing and imaging ash clouds from the August 7, 2008 eruption of the Kasatochi volcano in Alaska's Aleutian Islands. On August 27 I was able to capture this series of images showing the boundary between the ash layer still in sunlight and the layer darkened by Earth's shadow setting in the west, as the Sun continued its movement farther below the horizon. Sunset that day was 7:56 p.m. Central Daylight Time followed at 8:24 p.m. by the end of civil twilight. The series begins at 8:12 p. m. with the next three images taken at one minute intervals. During this time, the Sun moved from 3.9 to 4.5 degrees below my horizon. This sequence demonstrates that if a projection surface, like a stratospheric layer of ash, is present, the Earth's shadow can be seen briefly in the western sky.