寻找月亮

2021年7月11日

Find the Moon
Image Credit & Copyright: Jimmy Westlake (Colorado Mountain College)

Explanation: Where’s the Moon? Somewhere in this image, the Earth’s Moon is hiding. The entire Moon is visible, in its completely full phase, in plain sight. Even the photographer’s keen eye couldn’t find it even though he knew exactly where to look — only the long exposure of his camera picked it up — barely. Although by now you might be congratulating yourself on finding it, why was it so difficult to see? For one reason, this photograph was taken during a total lunar eclipse, when the Earth’s shadow made the Moon much dimmer than a normal full Moon. For another, the image, taken in Colorado, USA, was captured just before sunrise. With the Moon on the exact opposite side of the sky from the Sun, this meant that the Sun was just below the horizon, but still slightly illuminating the sky. Last, as the Moon was only about two degrees above the horizon, the large volume of air between the camera and the horizon scattered a lot of light away from the background Moon. Twelve minutes after this image was acquired in 2012, the Sun peeked over the horizon and the Moon set.

Tomorrow’s picture: comet, planet, or star?

寻找月亮
影像提供与版权: Jimmy Westlake (Colorado Mountain College)

说明: 月亮必然在这幅影像的某处，然而它到底在那？影像里的月亮一揽无遗极为明显，而且还是满相。摄影者其实完全知道该往何处找，不过就连视力极佳的他也见不到，只能借助相机进行长曝光取像才勉强找到月亮。现在你可为找到月亮的自己喝采，然而为何它会这么难找？理由之一：这幅影像是摄于月全食期间，而该时在地球影子里的满月，比正常情况下的满月要暗非常多。理由之二：这幅摄于美国柯罗拉多州的影像，取像的时间点在即将日出之前。此时与太阳180度反向的月亮，位在天空的另一侧，不过已沐浴在地平面下方的太阳之曙光里。最后一个理由：当时月亮悬在地平线上方2度，因此相机与月亮之间的厚厚大气，散射了月亮的大量月光。在拍下这张影像的12分钟之后，太阳浮出地平线，而月亮同时西沉。

明日的图片: comet, planet, or star?