100 Days Until Totality! 91 Days Left – Baily’s Beads and the Diamond Ring

Credit: Newbury Astronomical Society http://www.naasbeginners.co.uk/

The Moon is not a perfectly flat sphere. Instead, it is scarred with ancient meteor impacts, mountains, valleys, and canyons. When light from the Sun passes through these features, you might be able to observe an effect called Baily’s Beads, named after Francis Baily who first accurately described the phenomenon in 1836. Technically (and controversially), Edmond Halley made the first description of the event in 1715:

“About two Minutes before the Total Immersion, the remaining part of the Sun was reduced to a very fine Horn, whose Extremities seemed to lose their Acuteness, and to become round like Stars … which Appearance could proceed from no other Cause but the Inequalities of the Moon’s Surface, there being some elevated parts thereof near the Moon’s Southern Pole, by whose Interposition part of that exceedingly fine Filament of Light was intercepted.”

Pasachoff, J. M. (1999) “Halley and his maps of the Total Eclipses of 1715 and 1724” Journal of Astronomical History and Heritage’ (ISSN 1440-2807), Vol. 2, No. 1, p. 39-54

Right before and right after totality, you can also observe the Diamond Ring effect, which is when only a little bit of sunlight is passing by the Moon. Usually, the light passes through one major valley or canyon during this time, creating just one “bead.” This bead is the diamond on the ring.
Please note that while Baily’s Beads and the Diamond Ring occur near totality, they are NOT safe to observe with the naked eye.