Newtonian Reflectors
Newtonian reflector telescopes are the most cost effective type of telescope for astronomical observations, offering the lowest cost per unit of aperture. These telescopes are named for their inventor, the famed physicist Sir Isaac Newton. Newtonian reflectors are great for astronomical use, but are seldom used for terrestrial observation because they present an inverted image. This does not matter for astronomical use, as the notion of up vs. down is really just a matter pf perspective.