1- Determination of the ratio between the diameter of the shade of the Earth and the diameter of the moon :

• Choose one of the 4 photos from the eclipse
• Draw circles : choose radii randomly (in pixels) then click on "moon circle" or "earth shade circle".Then you can move the circle with the mouse. If the chosen radius is not good, do it again.
• With the help of the "computer" find the ratioearth shade radius on moon radius

2- Then you can find the distance between Moon and Earth and the Moon diameter.

• For that you can click on "HELP"

The point angle which the cone of shadow of the Earth makes is of 0.5° (it is the angle under which one sees 2 extreme rays of the Sun). It is easy to demonstrate the length OH of the cone of shadow is 114 X diameter of the Earth. OH = 114xAB

Knowing the ratio r = DE/CD measured with the circles and by using the similar triangles, one shows that the distance the EARTH-MOON :
AH' = AB X 114/(r+1).

Still using the similar triangles, we can demonstrate that the diameter of the Moon CD = AH'xAB/OH.

To verify results :
real diameter of the Moon: 3474.8 km
Earth-Moon distance on 3/03/2007 by midnight: 395 380 km