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
Types of trombone Types of trombone There are many different types of trombone. The most frequently encountered trombones today are the tenor and bass, though as with other Renaissance instruments such as the recorder, the trombone has been built in every size from piccolo to contrabass (pitch of brass instruments). See trombone for information about the instrument in general. The cimbasso is a brass instrument in the trombone family, with a sound ranging from warm and mellow to bright and menacing. It has three to six piston or rotary valves, a predominantly cylindrical bore, and in its modern incarnation is most often pitched