The telescope that Galileo presented to the Doge of Venice, and which was later lost, consisted of a tube of lead, with what is called a plano-concave eye-glass and a plano-convex object glass, and had a magnifying power of three diameters, which made objects look three times nearer than they actually were, and as a result nine times larger. The tube was about seventy centimeters long and about forty-five millimeters in diameter. It was first used in public from the top of the campanile in the piazza at Venice on August 21, 1609, and the most distant object that could be seen through it was the campanile of the church of San Giustina in Padua, about thirty-five kilometers away. As soon as Galileo returned to his home in Padua he busied himself with improving his invention. First he constructed a new telescope, which as he said “made objects appear more than sixty times larger.” Soon he had a still better one, which enlarged four hundred times. He used this to examine the moon, and said that it brought that body “to a distance of less than three semi-diameters of the earth, thus making it appear about twenty times nearer and four hundred times larger than when seen by the unaided eye.” To use the instrument more accurately he built a support which held it firmly. He had also now learned to make the lenses adjustable, by fixing the tubes that held them so that they could be drawn out of, or pushed into the main tube of the telescope. To see objects not very far distant very clearly he would push the glasses a little way apart, and to see things very far distant he drew the glasses together. But this last telescope did not altogether satisfy him, and so he built a still larger one. This brought objects more than thirty times closer and showed them almost a thousand times larger in size. With this he discovered the moons of Jupiter, and some of the fixed stars, and added much to what was already known concerning the Milky Way, a region of the sky which had long been a puzzle to astronomers. He spent a great part of his time now in his workshop, making and grinding glasses. They were expensive and very difficult to prepare properly. Out of more than one hundred that he ground at first he found only ten that would show him the newly found moons of Jupiter. The object glasses were the more difficult, for it was this glass which had to bring to a focus as accurately as possible all the rays of light that passed into the telescope.