All Figures

$\begin{figure} \par\includegraphics[width=14.7cm,clip]{2662fig1.eps} \end{figure}$ Figure 1: Optical layout of POLIS. Light enters the instrument at top right. F denotes the telescope focal plane. A collimator mirror forms an image of the entrance pupil near the rotating modulator, RM, and the scan mirror, SM. An imaging mirror re-images the solar image at F to the entrance slit, S, of the spectrograph. Slit jaw images are recorded from the reflective slit jaws of the entrance slit. The collimator re-images the entrance pupil to the grating, G. The dispersed beams are then re-imaged to the focal plane detectors, CCD 1 and CCD 2. A small pickoff mirror close the focal plane reflects the blue beam to CCD 2. Diffraction orders are isolated with narrow-band filters placed in front of each detector. Polarizing beam splitters placed directly in front of the CCDs separate the orthogonally polarized beams.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2662fig2.ps} \end{figure}$ Figure 2: Example of the gain table correction for the red channel, using data from August 2003. Image size $288\times 652$ pixel. Left: uncorrected image, I⁺ and I^- are separated spatially. Middle: Gain table. Right: Gain-corrected image. Profiles of each image from the marked row (short bar at left) are overplotted.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{2662fig3.eps} \end{figure}$ Figure 3: Stokes vector (I,Q,U,V) of a calibration measurement in the red channel. Solid: calibration input vector, calculated from the retarder and polarizer position angles. Squares: measured Stokes vector. Dash-dotted: Computed output vector $\vec{S}^{\rm out}_{\rm c}$ (Eq. (7)). Note the good agreement with the measured curve. Stokes Q is given in digital counts instead of the normalized intensity for a comparison with the corresponding number in the blue channel (cf. Fig. A.1).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{2662fig4.eps} \end{figure}$ Figure 4: Derivation of the retardance of the calibration waveplate. The matrix element $X_{\rm 3,1}$ of the instrument response function (Stokes $I\rightarrow U$ ) is plotted as a function of polarizer position angle for different values of the retardance. From the shape of the curves we find a "best'' retardance of 61.5 $^\circ$ . The fit error is indicated for the 61.5 $^\circ$ curve.
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In the text

$\begin{figure} \par\includegraphics[width=5.6cm,clip]{2662fig5.ps} \end{figure}$ Figure 5: Intensity map of sunspot NOAA 0425, observed on 9.8.2003, between 7:40 and 7:52 UT. Tick marks correspond to 1 arcs. Scan direction left to right, step width 0.35 arcs, 120 steps. The intensity gradient in scan direction is caused by the increase of intensity in the early morning. White crosses indicate the spatial positions of the profiles shown in Fig. 6.
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In the text

$\begin{figure} \par\includegraphics[width=15.5cm,clip]{2662fig6.ps} \end{figure}$ Figure 6: Stokes profiles measured in the red channel, top to bottom: I, Q, U, V each normalized to continuum intensity, $I_{\rm c}$ , of the quiet Sun profile. Left column: sunspot penumbra, middle column: umbra, right column: quiet Sun. The profiles were taken at the points marked with crosses in Fig. 5.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{2662fig7.ps} \end{figure}$ Figure 7: Scan of a small pore, observed on 15 Oct. 2003. Top to bottom: Stokes components I, Q, U and V. Left column: spectra of Fe I 630.15 and Fe I 630.25 nm, single scan step. Middle column: wavelength integrated maps of Stokes I, Q. U and V around 630.2 nm. The vertical black bar in I indicates the scan position of the spectra shown. Tick marks correspond to 1 arcs. Right column: spectra of the Ca II H line. The horizontal bar in the Stokes V spectrum marks the position of the profiles displayed in Fig. 8. Only the co-spatial field-of-view of blue and red channel is shown. The red channel has been rescaled to have the same spatial sampling of 0.29 arcsec per pixel.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{2662fig8.ps} \end{figure}$ Figure 8: Co-spatial profiles in red ( left column) and blue ( right column) channel of POLIS, top to bottom: Stokes I, Q, U and V. Data were taken on 15 Oct. 2003 at 15:30 UT, scan of a small pore. Note the opposite sign of the Stokes V signal in the calcium line core, compared to that of the photospheric lines in the wing of the calcium line or in the red channel. The apparent reversal is due to the emission profile in the calcium core that changes the sign of the circular polarization.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{2662fig9.ps} \end{figure}$ Figure 9: Simultaneous data from TIP and POLIS, showing part of active region NOAA 0484, observed on 20 Oct. 2003 at 10:11 UT at the VTT Tenerife. Tick marks are 1 arcs. Bottom row, left to right: intensity maps in Fe I 1565 nm (integrated over the line), continuum at 630.3 nm, and in the blue wing of the Ca II H 396.5 nm line. Top row, left to right: total circular polarization $\int \vert V\vert(\lambda) \rm d\lambda$ for TIP and the red channel of POLIS, intensity map of the H2v emission peak at 396.83 nm of the blue channel. The white cross marks the spatial position of the line profile shown in Fig. 10.
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In the text

$\begin{figure} \par\includegraphics[width=5.5cm,clip]{2662fi10.ps} \end{figure}$ Figure 10: Intensity spectrum of the blue channel corresponding to the strongest emission observed in the map of Fig. 9. Thin grey line: Liège atlas profile (Delbouille et al. 1973).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2662App1.ps} \end{figure}$ Figure A.1: Same as Fig. 3 for the blue channel, Stokes vector (I,Q,U,V) during the calibration. Solid: calibration input vector. Squares: measured Stokes vector. Dash-dotted: Computed output vector $\rm {\bf S}^{\rm out}_c$ (cf. Eq. (7)). Stokes Q is given in digital counts instead of the normalized intensity. Note that the observed polarization in QUV ( $\square$ ) has been multiplied with a factor of 10 for better visibility.

In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2662fig2.ps} \end{figure}$	Figure 2: Example of the gain table correction for the red channel, using data from August 2003. Image size $288\times 652$ pixel. Left: uncorrected image, I⁺ and I^- are separated spatially. Middle: Gain table. Right: Gain-corrected image. Profiles of each image from the marked row (short bar at left) are overplotted.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{2662fig4.eps} \end{figure}$	Figure 4: Derivation of the retardance of the calibration waveplate. The matrix element $X_{\rm 3,1}$ of the instrument response function (Stokes $I\rightarrow U$ ) is plotted as a function of polarizer position angle for different values of the retardance. From the shape of the curves we find a "best'' retardance of 61.5 $^\circ$ . The fit error is indicated for the 61.5 $^\circ$ curve.
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$\begin{figure} \par\includegraphics[width=5.6cm,clip]{2662fig5.ps} \end{figure}$	Figure 5: Intensity map of sunspot NOAA 0425, observed on 9.8.2003, between 7:40 and 7:52 UT. Tick marks correspond to 1 arcs. Scan direction left to right, step width 0.35 arcs, 120 steps. The intensity gradient in scan direction is caused by the increase of intensity in the early morning. White crosses indicate the spatial positions of the profiles shown in Fig. 6.
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$\begin{figure} \par\includegraphics[width=15.5cm,clip]{2662fig6.ps} \end{figure}$	Figure 6: Stokes profiles measured in the red channel, top to bottom: I, Q, U, V each normalized to continuum intensity, $I_{\rm c}$ , of the quiet Sun profile. Left column: sunspot penumbra, middle column: umbra, right column: quiet Sun. The profiles were taken at the points marked with crosses in Fig. 5.
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$\begin{figure} \par\includegraphics[width=5.5cm,clip]{2662fi10.ps} \end{figure}$	Figure 10: Intensity spectrum of the blue channel corresponding to the strongest emission observed in the map of Fig. 9. Thin grey line: Liège atlas profile (Delbouille et al. 1973).
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