Telescope vs Autocollimation - What's the difference?

As a verb telescope

is .

(physics|astronomy) the collimation of a telescope by means of a plane mirror.

(en noun)

A monocular optical instrument possessing magnification for observing distant objects, especially in astronomy.

Any instrument used in astronomy for observing distant objects (such as a radio telescope).

* telescopic * radio telescope * reflecting telescope * refracting telescope * terrestrial telescope

(telescop)

To extend or contract in the manner of a telescope.

To slide or pass one within another, after the manner of the sections of a small telescope or spyglass.

To come into collision, as railway cars, in such a manner that one runs into another.

(wikipedia autocollimation) (en noun)

(physics, astronomy) The collimation of a telescope by means of a plane mirror