Regarding groundbased observation , the largest optical telescopes to date are the twin 10 - m keck telescopes on mauna kea of hawaii.

位于夏威夷蒙那基亚山上的却克望远镜，口径达10米，是目前世上最大的光学望远镜。

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The groundwater observation well-network for earthquake prediction in China is the largest precursory observation system except the seismograph array.

中国地震地下水动态观测网是我国仅次于测震网的第二大地震前兆观测系统。

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"Fortunately, the largest patch of open water is in front of the observation window where visitors can see the swans and ducks at feeding time, " a spokesperson for the centre said.

BBC: Welney welcomes wildfowl that fled harsh Arctic weather