即使在莫纳克亚山，凯克也必须克服地球大气层的折射，这是地面望远镜最大的敌人。
Even on Mauna Kea, Keck has to deal with the distortion caused by Earth's gaseous atmosphere, which is the greatest enemy to ground-based telescopes.
这是由地球大气层顶部冰晶体折射太阳光而形成的，观测时间一般为日出或日落时，即太阳接近地面时。
It is caused by the reflection of sunlight from ice crystals and is most often observed at sunrise or sunset when the sun is low to the horizon.
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