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HDR: Earth's Circular Shadow on the Moon Explanation: What could create such a large circular shadow on the Moon? The Earth. Last week's full Moon -- the Buck Moon -- was so full that it fell almost exactly in a line with the Sun and the Earth. When that happens the Earth casts its shadow onto the Moon. The circularity of the Earth's shadow on the Moon was commented on by Aristotle and so has been noticed since at least the 4th century BC. What's new is humanity's ability to record this shadow with such high dynamic range (HDR). The featured HDR composite of last week's partial lunar eclipse combines 15 images and include an exposure as short as 1/400th of a second -- so as not to overexpose the brightest part -- and an exposure that lasted five seconds -- to bring up the dimmest part. This dimmest part -- inside Earth's umbra -- is not completely dark because some light is refracted through the Earth's atmosphere onto the Moon. A total lunar eclipse will occur next in 2021 May. HDR影像：月球上的圆形地球阴影 是什么在月球上形成了如此庞大的圆形影子？答案是地球。上周的满月是如此的圆，以至于它几乎正好与太阳和地球位于一条直线上。当这种情况发生时，地球会将其影子投射到月球上。亚里士多德对月球上的圆形地球阴影发表过评论，因此至少从公元前4世纪开始，人们就已经注意到了这一现象。新鲜的是人类用这种高动态范围影像来记录该阴影的能力。这幅呈现上周月偏食的精彩HDR影像由15张照片组合而成，其中包括一幅曝光时长短至1/400秒的照片，以避免过曝最亮的部分，以及一张曝光时长持续5秒的照片，以显示最暗的部分。地球本影中最暗的部分并不是完全黑暗的，因为有些光线是通过地球大气层折射到月球上的。下一次月全食将发生在2021年5月。 参考文献： https://apod./apod/image/1907/PartialLunarEclipse_Fattinnanzi_3345.jpg 近期文章： Astronomy Picture of the Day——首张黑洞视界尺度照片 |
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