Newtonian telescope secondary mirror. This design reduces the size and cost of the telescope with a shorter overall telescope tube length (with the corrector extending the focal length in a "telephoto" type layout) combined with a less costly spherical mirror. Commercially produced versions of this design have been noted to be optically compromised due to the difficulty of producing a correctly shaped sub-aperture corrector in a telescope targeted at the inexpensive end of the telescope market. 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
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,