When the concept of measurement is introduced in basic physics and astronomy courses, astronomical measurements are often reduced to examples of order-of-magnitude. On the other hand, there are descriptive approaches that do not put in contact the students with the instruments or with the objects of study. On the contrary, this work shows how an amateur telescope and a standard digital camera can be used to take images of the Moon, and obtain the distance to the satellite from them. The technique is based on a simple correlation analysis between two images taken from the same place with interval of some hours. The small variation in the angular size of the Moon due to the fact that the Moonobserver distance varies when the Earth rotates can be put in evidence, and serves to obtain the basic data to deduce the distance to the satellite.