A refracting telescope's light-gathering power is proportional to the size of the objective, or main, lens and to the ratio of the focal lengths of the objective lens and the eyepiece.
(A refracting telescope's light-gathering power; is; proportional to the size of the objective, or main, lens and to the ratio of the focal lengths of the objective lens and the eyepiece)
A refracting telescope's light-gathering power
is
proportional to the size of the objective, or main, lens and to the ratio of the focal lengths of the objective lens and the eyepiece