cross section of a reflecting telescope

Magnification depends on the length of the main tube and the power of the eyepiece.

eyepiece

Lens or system of lenses meant to magnify the image when placed before the eye.

light

Emitted by a celestial body, it crosses the main tube and is sent back by the concave primary mirror; the secondary mirror intercepts it and directs it toward the eyepiece.

concave primary mirror

Mirror that collects light and whose shape makes it possible to direct it toward the secondary mirror.

secondary mirror

Mirror that collects light and directs it toward the eyepiece.

main tube

The barrel of the telescope through which light rays travel; houses the optical system.