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
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