turbulence in the atmosphere. Limits a telescope's abilities. Can be magnified by a telescope
Size matters as far as light gathering ability goes. Sometimes a greater magnification just causes problems, though. And a larger scope can't necessarily magnify more. That is only controlled by eyepiece?
Color distortion. This applies to lenses only. Distortion in a lens when the focal lengths don't match up and the separate colors become visible.
Reflector telescope. Can tell because the eyepiece is positioned on the side. Flat mirror to reflect into eyepiece.
Reflector telescope. Uses a spherical mirror at the back and a flat mirror in the center (or flat for a Maksutov). Light bounces into the back then into the mirror in the center, then into the eyepiece.
The Catadioptic Telescope
Combo of the refractor and reflector. Also called a cat telescope. Uses a lens and a mirror as the main light gatherer.