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 cannon fact is precisely what conservation of momentum predicts. The principal difficulty is in keeping the configuration of the balls stable during the initial drop. Early descriptions involve some sort of glue/tape, tube, or net to align the balls. A modern version of the Galilean cannon was sold by Edmund Scientific Corporation and is still sold as the "Astroblaster". In this device, a heavy wire is threaded through all of the balls to keep them accurately aligned - but the principle is the same. The resulting rebound is quite powerful; in fact, eye safety issues became so prevalent that this toy