A Focal Curve Approximation of a Borromini Oval Contour

In this paper we derive a mathematical procedure for the determination of a Weberian focal curve (of two, three or four collinear foci), as a good fitting curve for the impost of the Dome of San Carlo alle Quatro Fontane by Francesco Borromini. For this research, the usual oval composition of two or more circles, which is a piecewise function having the property of C1 continuity, is substituted with a Weberian differentiable focal curve. The created procedure iteratively determines the position of foci giving the highest possible value of the coefficient of determination for the particular case study.