Glossary term: 天頂
Description: 天頂定義為觀測者正上方的一點，因此這個點隨著觀測者位置的變化而變化。例如，對位於倫敦、北京與開普敦的觀測者來說，他們的天頂是各不相同的。若用角度來度量，則天頂與觀測者的地平線成90度。天頂角定義為天體與天頂之間的角距離。位於天頂的天體的天頂角為0度，而位於地平線上的天體的天頂角為90度。與天頂相對的一點，即觀測者的正下方，稱為觀測者的天底。如果地球是一個完美的球體，那麼觀測者的天頂和天底之間的連線就會穿過地心，但實際上地球只是近似於球體，因此地心與這條連線通常有一定的距離。
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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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