What is the use of astronomical telescope?

Explanation

An astronomical telescope is used to get the magnification of distant astronomical objects like stars, planets, moon etc. the image formed by astromonical telecsope will be inverted. It has an obective of long focal length and a much larger aperture than the eyepiece. Light from a distant object enters the objective and a real image is formed in the tube at its second focal point. The eyepiece magnifies the image producing a final inverted image.

Magnification of astronomical telescope
The magnification m is the ratio of the angle `beta` subtended at the eye by the final image to the angle `alpha` which the object subtends at the lens or the eye.
`m = (beta)/(alpha)`
From the diagram, `m = (h//f_(e))/(h//f_(0))`
`m = (f_(0))/(f_(e))`
The lenght of the telescope is approximately, `L = f_(0) + f_(e)`