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second contact 【天文學】蝕既。

second cousin

Even with the much closer venus , the observations were tricky ; it was crucial to know the exact geographic positions of the observing stations and to accurately time the four “ contacts ” between venus and the sun . ( the first and second contacts occur at ingress , when venus ' s disk touches the sun ' s from first the outside and then the inside ; the third and fourth contacts occur at egress . ) but the potential payoff from the observations would be enormous 即使是距離近得多的金星,這個測量也不容易;必須要知道觀測站確實的地理位置,且要能準確測定凌日時金星和太陽發生四次接觸的時間(第一和第二次接觸發生在初切,即金星的盤面由外然后再內接觸到太陽盤面;第三和第四次接觸發生于終切) 。

Second contact surface 第二界面

Second contact with master 第二次接觸

We must not forget to open the aperture at the second contact . 在食既時不要忘記放大光圈。