AFOSC POLARIMETER
=================

  Instrument Overview                                                         
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    The Asiago Faint Object Spectrographic Camera (AFOSC) Polarimeter consists
    of a double Wollaston prism which splits the incoming light into four     
    polarized beams at 0, 45, 90, and 135 degrees, separated by 20 arcsec.    
    These four beams are sufficient to determine the Stokes parameters I, Q,  
    and U simultaneously with a single exposure.                              
                                                                              
    The CCD has 1024x1024 pixels (the pixel size is  24 microns), providing a 
    total field of view of 18.14x18.14 arcmin, with a pixel scale of 0.473    
    arsec/pixel.  The input field has been masked at the telescope focal plane
    by a field selective mask to avoid the overlap of the final images on the 
    CCD detector.                                                             
                                                                              
    The four output beams emerge collimated from the double Wollaston prism   
    and are then focused on the CCD detector by the focal camera of AFOSC.    
    The final image is formed by four strips from which the I, Q, and U       
    parameters can be extracted.  From analysis of several polarized and      
    unpolarized standard stars, it is seen that the instrumental polarization 
    is fairly constant and always below 0.4 percent, while the systematic     
    errors in the position angle are below 1.5 degrees.

References
==========

Desidera, S., E. Giro, U. Munari, Y.S.  
        Efimov, A. Henden, A. Benetti, T. Tomov, A. Bianchini, and C.         
        Pernechele, Polarimetric evolution of V838 Monocerotis, Astron.       
        Astrophys. 414, 591-600, 2004.

Pernechele, C., E. Giro, and D.         
        Fantinel, Device for optical linear polarization measurements with a  
        single exposure, Proc. SPIE 4843, 156-163, 2003.