On the use of Bowen compensators for polarimetry

Universitäts-Sternwarte, Geismarlandstr. 11, D-37083 Göttingen, Germany

Send offprint request to: M. Koschinsky

Received: 16 January 1996
Accepted: 9 February 1996

Abstract

For high precision polarimetry it is very desirable to observe with a telescope that is free of instrumental polarization. Yet it is often inevitable to introduce optical devices which generate crosstalk between the Stokes components and the V component due to phase retardations upon reflection at mirror surfaces. We show that Bowen compensators are well suited to compensate for these phase changes. They consist of 2 rotatable phase retarder plates, and it can be shown that they act on polarized light either by a rotation of the axes of the polarization ellipse followed by a prescribed, desired phase change or by a phase change followed by rotation of the ellipse. We present applications of Bowen compensators in the Gregory Coudé Telescope at the Observatorio del Teide/Tenerife.