Exploration of the Moon invention of the telescope, an increasing number of people began to recognise the Moon as a sphere, though many believed that it was "perfectly smooth". In 1609, Galileo Galilei drew one of the first telescopic drawings of the Moon in his book and noted that it was not smooth but had mountains and craters. Later in the 17th century, Giovanni Battista Riccioli and Francesco Maria Grimaldi drew a map of the Moon and gave many craters the names they still have today. On maps, the dark parts of the Moon's surface were called "maria" (singular "mare") or seas, and the
Lovell Telescope from these original objectives, and are outlined in the following sections. In Autumn 1958, the telescope was used to bounce "Hellos" off the Moon for a demonstration in Lovell's third Reith Lecture. The telescope was also used to receive messages bounced off the Moon (a "moonbounce") as part of the 50th anniversary First Move festival. In April 1961, a radar echo from Venus was achieved using the telescope while the planet was at a close approach, confirming measurements of the distance of the planet made by American telescopes. The 21 cm hydrogen line was discovered during the telescope's construction; the