Theopeningpartoftheweightshouldbeplacedsymmetricallytoreducethetangentialdeformationasmuchaspossible,sothattheweightoftheweightisverticaldownward.;观察标尺时不要忽高忽低引起视差,眼睛要正对望远镜

  尔雅 智慧树 mooc


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