We cannot interchange the objective and eye lenses of a microscope to make a telescope. The reason is that the focal length of lenses in microscope are very small, of the order of $\mathrm{mm}$ or a few $\mathrm{cm}$ and the difference $\left(f_0-f_e\right)$ is very small, while the telescope objective have a very large focal length as compared to eye lens of microscope.