The above image is one in a series
analysed with ImageAnalyst to find a
best fit circle to the umbra edge and to give the semi-diameter of
the umbra. All images were measured to produce a plot of the change
of semi-diameter during the first half of this eclipse as shown
below:
A best fit polynomial (black line) suggests that the measured semi-diameter changed during the first half of the eclipse of up to 0.5 degrees due to the curvature of the Moon's surface and to possible changes in the size of the umbra.
F2 is the expected umbral semi-diameter
.gif)
In the above Excel Chart the computed values of delta and Fi are compared with the measured semi-diameter of the Umbra (Fm).
Delta is the slope of the umbra edge to the Earth-Moon axis and Fi is the computed topocentric umbral semi-diameter all in degrees. The difference between Fi and Fm indicates the real change in the umbra during the first half of this eclipse.