ZIMPOL Stokes images containing different limb distances (left) and example spectra at specific locations (right). Four left panels: I, Q/I, U/I, and V/I (top to bottom, respectively) Stokes images after the data reduction. The CLV is along the spatial pixels of the camera. Three spectral regions are identified in the images: Sr I, Fe I, and continuum, indicated by the colored dotted vertical lines (Sr I = magenta, Fe I = cyan, continuum = orange). The limb position is indicated by the horizontal orange-red dashed line. Right panels show example spectra: Stokes I and Q/I close to the limb (together with the spectra given in the Second Solar Spectrum atlas by Gandorfer 2002), Stokes U/I and V/I in a magnetically active region (position indicated by the purple lines in the left images). The Q/I in the Sr I region is fitted with a Gaussian, while V/I in Sr I and Fe I is fitted with a Gaussian derivative. Regions that are averaged for further data analysis are indicated by the light orange bands.