Newtonian telescope Newtonian telescope The Newtonian telescope, also called the Newtonian reflector or just the Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton (1642–1727), using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design makes it very popular with amateur telescope makers. Newton's idea for a reflecting telescope was not new. Galileo Galilei and Giovanni Francesco Sagredo had discussed using a mirror as the image forming objective soon after the invention of the
Galilean invariance a Galilean transformation. In other words, all frames related to one another by such a transformation are inertial (meaning, Newton's equation of motion is valid in these frames). In this context it is sometimes called "Newtonian relativity". Among the axioms from Newton's theory are: Galilean relativity can be shown as follows. Consider two inertial frames "S" and "S' ". A physical event in "S" will have position coordinates "r" = ("x", "y", "z") and time "t" in "S", and "r' " = ("x' ", "y' ", "z' ") and time "t' " in "S' ". By the second axiom above,