因此，中性滤光片和光谱片的位置控制就显的尤为重要。

So the control of their position seems very important especially.

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普通相机用滤光片来阻隔红外光谱范围内的任何光线。

Ordinary cameras use filters to block any light in the infrared spectrum.

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第一章幻灯片是在,实验室里氦，氦钙以及钠的光谱。

The first slide is a spectrum made in the laboratory of hydrogen, helium and calcium and sodium.

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