Problem 5.47

At what magnification $\Gamma$ of a telescope with a diameter of the objective $D=6.0 \mathrm{~cm}$ is the illuminance of the image of an object on the retina not less than without the telescope? The pupil diameter is assumed to be equal to $d_{0}=3.0 \mathrm{~mm} .$ The losses of light in the telescope are negligible.