Newtonian Telescope

The telescope is an optical device that increases the viewing angle when viewing distant objects. The main parts of the telescope are the objective lens and the eyepiece.

Newtonian telescope belongs to the group of reflectors, because the objective lens is formed by a hollow (concave) mirror. Compared to a refractor, the lenticular lens of this type of telescope is replaced by a hollow mirror forming a real image, which is observed through the eyepiece lens. Parallel rays falling on the mirror are concentrated in its focus. Rays are deflected by a plane mirror outside the telescope tube in order to better observe the created image.

The advantage of this type of telescope is less of the imaging defects than with the refractors (lens telescopes). Since the light from the mirror merely reflects, but does not pass through it, it does not cause e.g. the chromatic aberration common for lenses.

The downside is that in order to achieve a quality picture, a large radius of the telescope mirror is required.