Sentence Examples


  • The triple object-glass, consisting of a combination of two convex lenses of crown glass with a concave flint lens between them, was introduced in 1765 by Peter, son of John Dollond, and many excellent telescopes of this kind were made by him.
  • If then the objective tube is directed to any star, the convergent beam from the object-glass is received by the plane mirror from which it is reflected upwards along the polar axis and viewed through the hollow upper pivot.
  • Telescope with a concave eye-lens instead of an eye-piece still survives as the modern opera-glass, on account of its shorter length,_ but the object-glass and eye-lens are achromatic combinations.
  • It may be fixed at the end of a tube, of a suitable length to its focal distance, as an object-glass, - the other end of the tube having an eye-glass fitted as usual in astronomical telescopes.
  • Pp. 199-209) the rays from the object-glass pass successively through lenses as follows: The lens b is divided, and one of the segments is moved by a micrometer screw.