Baily's Bead closeup
This photograph was taken with a Canon 40D camera with a Canon 100-400mm IS Lens with a 1.4x extender, effective focal length of 560mm and aperture f/8. The camera and lens were mounted on a tripod.
The exposure time was 1/2000s at ISO 200. The image was cropped to bring out the Baily's Beads and the prominences on the limb of the sun. No filter was used (and the UV filter was removed to reduce reflections in the optics).
During the partial phase of the eclipse it is essential to use a filter to prevent damage to the eye and the camera. I use a Thousand Oaks black plastic filter to remove 99.999% of the sun's energy. Once the Diamond Ring is about to happen, then it is safe to remove the filter and capture Baily's beads (though it is not safe to see them with the naked eye) and the total eclipse itself.
The beads are due to light from the sun shining through the lunar mountains and valleys on the Moon's limb and creating a "bead" like effect thats last a few seconds.