  The value of the eclipse solar radius during the 2017 August 21 total solar
eclipse was estimated to be $S_{\odot} = (959.95\pm 0.05)"$ at $1\,au$ with no
significant dependence on wavelength. The measurement was obtained from the
analysis of a video of the eclipse flash spectrum recorded at the southern
limit of the umbral shadow path. Our analysis was conducted by extracting light
curves from the flash spectrum and comparing them to simulated light curves.
Simulations were performed by integrating the limb darkening function (LDF)
over the exposed area of photosphere. These numerical integrations relied upon
very precise computations of the relative movement of the lunar and solar
limbs.
