星空故事：天上人間

放大圖片

　一般人以為，在晴朗的晚上，只要找到北斗七星就能確定北極星的方位，從而辨別方向；可時值深秋，從傍晚至深夜，北斗始終位於香港的地平以下，起碼要等到明年的二月，大家才能有緣在入黑後目睹北斗七星。那麼在這個季節的晚間，怎樣才可以找出北極星呢？原來與北斗隔著北極星遙遙相對的是仙后座，故此當北斗沉於地平之下，仙后卻高掛北面的天空。

　仙后座算是一個頗為容易辨認的星座，她有5顆頗明亮的光星，排成現今小孩最早學會的第一個英文字母──M。只要用兩條假想線把M的第一隻角等分成三份，靠內的一條線便直指向北極星（見圖）。在希臘的神話裡，仙后座屬王族星座，與一個斬妖除魔的故事有關。

Cassiopeia, the heavenly Queen

　Many people thought they could identify the cardinal points with the Big Dipper.This is only partly right. Firstly, you would not be able to see any constellations under the heavily polluted Hong Kong sky. Secondly, even if you venture into the country park, you would not be able to spot the Big Dipper at this time of the year. But the Big Dipper is not the only guide to the North Star. On the opposite side of the Big Dipper sits Cassiopeia, a member of the royal family dwelling in the northern sky. Cassiopeia's 5 fairly bright stars are so arranged that even the youngest children could recognize her pattern right away—the renowned ‘M’. Trisect the first angle of the ‘M’ and the inner trisector points almost directly at Polaris.　■甄枝強 資深天文愛好者