Variation of the projected semi-major axis of an ellipsoid along its symmetry axis for 5 different values of its ellipticity (labeled in blue) with its major axis inclination. The observed semi-major axis of 4.″9 of FH Ser is marked by a solid vertical line, with 1-σ uncertainty marked by vertical dotted lines. The black dot corresponds to the best fit value, with blue dots in the left and right panels representing acceptable values within the uncertainty of the observed parameters.