Optics.
the ratio of the angle subtended at the eye by the image formed by an optical instrument to the angle subtended at the eye by the object being viewed.
Optics.
the ratio of the angle subtended at the eye by the image formed by an optical instrument to the angle subtended at the eye by the object being viewed.
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012