Definition of Ramsden in English:

Ramsden

noun

Optics
  • Attributive and (now rare) in the genitive. Designating an eyepiece consisting of two planoconvex lenses of equal focal length with their convex surfaces towards each other and a separation less than their focal length.

Origin

Late 18th century; earliest use found in Philosophical Transactions of the Royal Society of London. From the name of Jesse Ramsden, English instrument-maker, who described the eyepiece in 1783 ( Philos. Trans (Royal Soc.) 73 94).

Pronunciation

Ramsden

/ˈramzdən/