Timing Baily’s Beads during the August 21, 2017 Total Solar Eclipse

Precise timings of beading phenomena made near the northern and southern limits of the umbral path (i.e., the graze zones), may be useful in determining the diameter of the Sun relative to the Moon at the time of the eclipse. Such measurements are essential to an ongoing project to try to detect changes in the solar diameter.

Because of the conspicuous nature of the eclipse phenomena and their strong dependence on geographical location, scientifically useful observations can be made with relatively modest equipment.  For more detailed information on observing techniques for Baily’s Beads, see the information in the free IOTA Observer’s Manual (Chapter 11 specifically covers Solar Eclipse observing).

For more information contact:

Richard Nugent at