SOHO uses an internal occulting disk

SOHO uses an internal sun-shade known as an occulter to view the corona, but diffraction of stray light limits the area that can be observed. The bright circle within the dark disk shows the actual size and position of the Sun. SOHO's occulter covers twice the diameter of the Sun. The external coronagraph planned for Proba-3 will cover only 1.05 solar radii, or even less, so a previously hidden section of the corona will be visible on a sustained basis.

The Sun unleashed a large (X-3 class) solar flare December 13, 2006 along with a coronal mass ejection (CME) that appears to be headed towards Earth. The source of these eruptions was the very active sunspot region 930. A shower of high-energy particles appeared as specks and white streaks on the imagers aboard SOHO, the primary watchdog for solar storms. The video clip from LASCO C2 coronagraph shows a CME emerging from behind the occulting disk and then almost immediately the imager is being struck by the particles (that travel at half the speed of light).