A polarimeter for monochromatic studies of solar prominences

Abstract

The photoelectric polarimeter which is described associates the three major discoveries of B. Lyot: the coronagraph, the birefringent filter and the polarimeter. However it differs completely from the coronameter. It is possible to study many emission lines by tuning the birefringent filter. But the D3 helium line is mainly used. In 10 s of time, the polarimeter measures in a 5" diameter spot three quantities: monochromatic intensity, polarization ratio p, angular deviation from the limb: e. The instrument gives a polarimetric map of the prominence. Owing to its performances, it is possible to study fast moving objects such as active prominences.