Glossary term: 天底
Description: 天底定義為觀測者正下方的一點。這個點是隨觀察者位置的變化而變化的。對位於倫敦的觀測者來說，他的天底與位於北京或開普敦的觀測者的天底是不同的。若用角度來度量，則天底與地平線成90度。與天底相對的一點稱為天頂。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
This is an automated transliteration of the simplified Chinese translation of this term
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