John Wall refractor

The John Wall telescope is a 30-inch f/12 refractor. In the entire 400-year history of astronomical telescopes, this is by far the largest refractor (lens telescope, as distinct from a reflector, which uses a concave mirror to do the same job) ever constructed by a single individual. Even today, it ranks as the equal-5th largest refractor anywhere in the world - the largest being only a 40-inch - and the largest ever operated in the British Isles; the last time another refractor as big as this was built (the Thaw photographic telescope, Allegheny Observatory, USA) was in 1914!

The John Wall 30 inch refractor

The John Wall 30-inch refractor.

That 'single individual' is John Wall, telescope maker extraordinaire and inventor of the 'Crayford' eyepiece-focusser. John did all the development of this wildly unconventional approach to large refractor building, the detailed design-work and all its actual fabrication, both mechanical and optical, single-handedly, in a tiny back-garden workshop and mostly using materials commonly available in the engineering and building trades.