A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2017 Aug 18, 23:17 -0700
Bill B, you wrote:
"the semi diameter of the moon at full totality will be larger than the sun's, so a pretty sweet view for those lucky enough to be centered in the path."
In fact, that simple condition, SDmoon > SDsun, is the actual defining condition for a total solar eclipse. If it's the other way around, then you get an annular eclipse which is just a flavor of partial eclipse with none of the drama or beauty of a total solar eclipse. You only get a total solar eclipse when the Moon completely covers the brilliantly bright photosphere of the Sun leaving behind the ghostly corona. When the Moon is a bit too far from the Earth, implying a lower apparent diameter (and in CN terms quantified by a lower HP which is directly proportional to SD), it does not cover the photosphere and the Sun is only reduced in brightness by 5 or 6 magnitudes. An annular eclipse like that is interesting to the eclipse afficionado, another box to check off, but much less impressive than a total eclipse.