They are able to do so because these records use both compass bearings and astronomical observations to locate a vessel.
他们之所以能够那样做，是因为这些原始记录同时使用了罗盘方位于天文观察来定位一艘航海船。
The main product has telescope, astronomical telescope, night vision, magnifier, microscope, compass etc., are various to optical device and accessions.
主要产品有望远镜、天文望远镜、夜视仪、放大镜、显微镜、指南针等各种光学器材和配件。
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