The telescope in the making, the Galileo first telescopic observations

In the first part of this paper we briefly discuss some historical constraints useful for understanding when Galileo for the first time aimed his telescope to the Moon which most probably was the first astronomical object observed by the Scientist. In the second part we discuss the dates of the observations on which the etchings, published in the Sidereus Nuncius, are based. It results that the five etchings refer to observations performed in December 1609 and January 1610. The measurement of the position, of some peculiar structures of the lunar surface clearly represented by Galileo in the etchings, shows that he was very careful in trying to produce a faithful graphical rendering of what he was observing.