Answer:
Light enters the telescope and reflects off a rough concave mirror at the back of the telescope.
Step-by-step explanation:
The chromatic aberration plaguing the observation early astronomers was studied by Sir, Isaac Newton and found to be created by the passage of light through a lens as such Newton's solution was to simply take out the lens from the telescope and replace them with polished metal mirror.
The reflecting telescope was built by Sir Isaac Newton with a purpose of proving the theory of the spectrum of colors composed in white light.