An Etymological Dictionary of Astronomy and Astrophysics

An → optical system in which the → beam of light from the → primary mirror is reflected down through the instrument’s → polar axis by a path bent like an → elbow.
Since the focus remains fixed with respect to the Earth, light can be analyzed with permanently installed instruments. In addition long → focal lengths allow higher → spectral dispersions.

Etymology (EN): From Fr. coudé “elbowed,” from coude “elbow,” L. cubitus; → focus.

Etymology (PE): Kânun, → focus; ârenjvâr “elbow-like,” → elbow.