Walter Lewin, though, has asked APOD to pose this as a challenge to astrophotographers: create a real single-exposure image of a clear night sky that features 360 degree star trails.
沃尔特·卢因通过APOD向广大天体摄影师发起挑战——拍摄一幅360度星流迹的单曝光晴朗夜空照片。
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The sky in the exposures was de-rotated to compensate for the rotation of Earth, then images were stacked together producing an image identical to a singleexposure but with less digital noise.