In 1930, a Pittsburgh plumber built a tiny aluminium observatory in his backyard for a homemade telescope; its unusual dome became a prototype for observatory designs and later helped bring him face to face with Einstein

• In the autumn of 1930, Leo Scanlon, a plumber from Pittsburgh, solved a problem in his backyard that would leave a lasting mark on amateur astronomy.
• Scanlon was building a private observatory behind his home in the Summer Hill neighbourhood on Pittsburgh's North Side.
• He needed a lightweight, weather-resistant dome to protect a homemade telescope.