地球的本影--月全食疊加影像

barying · 發表於 2011-12-16 05:49:29

地球的本影

地球影子黝黑的中心區稱為本影 (umbra)，是個延伸到太空的錐狀暗區，在月食時最容易見到它渾圓的切面。舉例來說，上星期六滿月切進地球本影的南緣，讓大部份地區得以見到月全食。月亮總共花了51分鐘在本影內，這也是此次月全食食甚階段的長度。上面這幅從中國北京拍攝的影像，疊加了數張連續的全食和偏食階段照片，以展現地球本影弧狀的邊緣、月亮所在距離的地球本影之相對大小、以及月球切入本影的過程。在較暗的全食階段時，依稀可見到背景恆星。

The Umbra of Earth
Image Credit & Copyright: Wang, Letian

原文：
Explanation: The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. For example, last Saturday the Full Moon slid across the southern half of Earth's umbral shadow, entertaining moonwatchers around much of the planet. In the total phase of the eclipse, the Moon was completely within the umbra for 51 minutes. Recorded from Beijing, China, this composite eclipse image uses successive pictures from totality (center) and partial phases to trace out a large part of the umbra's curved edge. Background stars are visible in the darker eclipse phases. The result shows the relative size of the shadow's cross section at the distance of the Moon, as well as the Moon's path through Earth's umbra.
原文網址：http://apod.nasa.gov/apod/ap111215.html

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