Isaac Newton built his reflecting telescope as a proof for his theory that white light is composed of a spectrum of colours. He concluded that the lens of any refracting telescope would suffer from chromatic aberration and chose mirrors to bypass that problem entirely.
Newton used a custom composition of metal consisting of six parts copper to two parts tin known as speculum metal. He shaped this object-metal to be two inches broad and about one-third part of an inch thick to prevent bending.
Newton completed his first reflecting telescope in late 1668 and first wrote about it in a letter dated the 23rd of February 1669 to Henry Oldenburg. The instrument had a diameter of about 25 English Inches and magnified between 30 and 40 times according to Newton's own measurements.
Isaac Barrow showed the telescope to a small group from the Royal Society of London at the end of 1671 and they demonstrated it for Charles II in January 1672. The telescope remained in their repository until it disintegrated and disappeared from records with the last reference occurring in 1731.
F.L. Agate made a replica of the 1668 Newton's telescope in 1924 for the Science Museum London. Two additional replicas were made in the 1960s for the Queen and the European Northern Observatory while another was constructed in 1984 for the chief designer of the William Herschel Telescope.