Arago cyanopolarimeter

The instrument consists of an optical tube that has a set of glass plates at one end (polarizer) and a Nicol prism in the eyepiece (analyzer). The angle of the polarizer can be adjusted and measured on a semi-circular graduated circle (105°-0-105°, divided in single degrees). The polarizer slides on a horizontal rod to position it at various distances from the optical tube. Another graduated circle, made of four 90 degrees quadrants, divided in single degrees, is used with a bubble level to determine the instrument angle of inclination. A piece of black fabric on two rollers, extending from the end of the optical tube to the polarizer, was used to eliminate unwanted glare. The instrument is set on a telescoping stand supported by a tripod.