A sun diagonal (Herschel's wedge) made by John Browning, London, circa 1880.
Length: 8 cm.
For a similar Sun Diagonal by John Browning see the collection of the Museum of Applied Arts & Sciences, Sydney, Australia. Object No: H10025 https://collection.maas.museum/object/230591
A Herschel wedge or Herschel prism is an optical prism used in solar observation to refract most of the light out of the optical path, allowing safe visual observation. It was first proposed and used by astronomer John Herschel in the 1830’s.