If you have glasses you know that optically focus has to do with bringing the light to a focal point in the back of your eye.

如果您戴眼镜，您就会知道，从光学的层面理解，焦点的意思是，将光线汇聚到您眼底的一点上。

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This is the distance (usually in mm.) from the lens (or primary mirror) to the point where the telescope is in focus (focal point).

就是从透镜(或者主反射镜)到焦点的距离，通常单位是毫米(mm)。

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You need a focal point - like when a photographer chooses the central subject of a picture, the primary object on which all eyes focus.

你需要重点式选择时的中心主题摄影图片、主要对象是所有目光的焦点。

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