Write a note on astronomical telescope.

An astronomical telescope is an optical instrument which is used to see the magnified image of distant heavenly bodies like stars, planets, satellites and galaxies etc.

The final image formed by an astronomical telescope is always virtual, inverted and magnified.

Principle: An astronomical telescope works on the principle that when an object to be magnified is placed at a large distance from the objective lens of telescope, a virtual, inverted and magnified image of the object is formed at the least distance of distinct vision from the eye held close to the eye piece. Figure below shows the astronomical telescope.

Working: Parallel rays of light coming from the distant object forms real, inverted and diminished image of an object.

This image acts as an object for the eye piece. The eye piece than forms virtual, erect and magnified image of the distant object.