During the eclipse process, the moon slowly begins to cover the sun. This is the first sign of a Baily's Bead. One or more may slowly develop or recede as long as 20 minutes before or after central eclipse. The real action happens within several minutes before 2nd contact when one or more beads begin are clearly visible. Our sites are typically located 1-3km inside the path of the eclipse from the edge.
Totality lasts only a fraction of the time at the central line for total eclipses.
But for annular eclipses, the sun is not completely eclipsed and the corona is not visible. Hence, you do not give up much at an annular eclipse to watch from the limit line. To gather data for a complete solar diameter analysis, observers must watch from both the northern and southern edges of the eclipse path. Locating the exact sites is vital and is accomplished by our use of Global Positioning System receivers. In panel 3 just to the right of bead 5 are two dim beginnings of beads 6 and 7 that are distinct in panel 4.