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。

youdao

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)。

youdao

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)。

youdao