I am trying to measure the charge(or voltage) of a positively charged sphere by touching it with a non- calibrated electroscope. I am getting consistent results in the separation(or angle) between the metal leaves, but I don´t know how to calculate the voltage between the leaves from there. I thought of considering the point at the end of each metal leaf as a "point charge", as if my electroscope was made of two metallic spheres instead of two foils. That's the only method I have found in the internet. My question is, is there any method (or formula) that will give me the potential between two leaves in an electroscope given their material, mass, length and the angle they form?