The quantitative study of the solar corona between 3 and 20 R⊙ is still a challenging task. Inherent difficulties are the proximity of the Sun and the still bright inner corona (< 3 R⊙), the low brightness of the outer corona and the low contrast of possible structures. A spinning, externally-occulted coronograph having its field-of-view limited to a sector of the corona presents several advantages over conventional coronographs for this study such as higher rejection of stray light and azimuthal uniformity over the whole field-of-view. Such an instrument could address the following aspects of the F-corona:

– photopolarimetry and colorimetry

– ellipticity, axis of symmetry

– temporal/spatial variations

– equatorial enhancements (rings)

– local component.