As Venus was closer to the Earth, its parallax angle would be larger, and Halley worked out that by using Venus it would be possible to measure the Suns distance to 1 part in 500.

由于金星离地球更近，所以它的视差角会更大。哈雷计算出，利用金星可以测量出太阳与地球之间的距离，误差为五百分之一。