Unlike others, Tele Vue prisms and mirror diagonals begin life as one solid chunk of metal-which is then continually refined to produce what you see before you now. This is a huge asset because there's nothing within the prism or diagonal which could unscrew and cause a heavy, expensive eyepiece to drop.
The 45° Erecting Prism gives an upright but laterally reversed image, which great for stargazing. Prisms and diagonals with 45° viewing angles offer simple shared viewing for observers of differing heights.
