Correct the following sentence:

The objective of telescope has small aperture.

Correct the following sentence:

For a simple microscope with image at infinity the magnifying power $M$ is given as $M = \left(1+D\right)/f$, where $D$ is the distance of distinct vision and $f$ is the focal length of the lens used in simple microscope.

Correct the following sentence:

A person suffering from long sight uses convex lens.

Correct the following sentence:

The distance between objective and eye-piece of an astronomical telescope for normal vision setting is $\left(f_o+f_e\right)/2$.