Portable reflecting telescope, c 1767.
© Science Museum / Science & Society Picture Library
This reflecting telescope can be used with any one of three different optical configurations (Gregorian, Casegrainian or Newtonian) by replacing the smaller mirror. It was made by James Short (1710-1768), then the foremost optical instrument maker in London, and has a nine inch (229 mm) speculum metal mirror. The telescope is mounted on Short's so-called 'universal'; a portable equatorial stand with a wooden fork holding the tube and an adjustable polar axis. The whole wooden framework moves on wheels and has carrying rods like a sedan chair. Selling for several hundreds pounds, a considerable sum at the time, this extravagent telescope would probably only have been purchased by wealthy amateurs.