当然用装在三角架上的照相机固定摄影，长时间曝光能拍到星星因地球自转而形成的同心圆轨迹。

Of course, with the camera fixed to a tripod, the stars themselves produce concentric trails in long exposures, a reflection of the Earth's rotation around its axis.

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绝大多数的数码相机都能曝光30秒而不会产生过多的噪点，这是一个很好的起点，这个曝光时间也可以避免拍下星星因地球自转产生的轨迹。

Most digital cameras can easily a handle a 30-second exposure before noise starts getting out of hand. That's a great place to start.

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