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
Electric instrument Electric instrument An electric musical instrument is one in which the use of electric devices determines or affects the sound produced by an instrument. Electric musical instruments are an example of electric music technology. It is also known as an amplified musical instrument due to the common utilization of an electronic instrument amplifier to project the intended sound as determined by electric signals from the instrument. Two common types of instrument amplifiers are the guitar amplifier and the bass amplifier. This is not the same as an electronic musical instrument, like a synthesizer, which uses entirely electronic means to both