  On January 20th, 2019, a total lunar eclipse was possible to be observed in
Santiago, Chile. Using a smartphone attached to a telescope, photographs of the
phenomenon were taken. With Earth's shadow on those images, and using textbook
geometry, a simple open-source software and analytical procedures, we were
allowed to calculate the ratio between the radii of the Moon and the Earth. The
results are in very good agreement with the correct value for such ratio. This
shows the strength of the smartphone technology to get powerful astronomical
results in a very simple way and in a very short amount of time.
