RMS intensity contrast variation with slit position (upper panel) and power spectrum of the intensity at the center of the Sr I line (lower panel). For the latter, the black dots show the power spectrum windowed by a Hann filter before computing the FFT, summed over all scan positions. The solid blue line shows a median filter applied to the Hann-windowed power spectrum. The vertical dashed red line indicates the frequency that equates to an effective spatial resolution of 0$\stackrel{″}{.}$2.