There are two main flavors of telescope: refractors, which use a lens, and reflectors, which use a mirror.

使用透镜的折射镜和使用单面镜的反射镜。

'Let me collect myself; he is going to the observatory of Cambridge, United States, to meet some gentlemen there, and spy through the great refractor.

“让我冷静下来；他要去美国剑桥的天文台，会见那里的一些先生，并通过大折射镜进行观察。