The history of the telescope in relation to the development of astronomy, from the invention of the refractor at the beginning of the seventeenth century, through its application as a telescopic sight on observatory instruments and the application of achromatic lenses from the mid-eighteenth century. In parallel, the story of the reflector is traced from Newton and others in the seventeenth century, through its use outside professional astronomy in the eighteenth century and its development into large instruments by William Herschel. The large reflector remained principally an instrument of wealthy amateurs until the early twentieth century.