Excerpt from The Private Life of Galileo By Galileo Galilei, Maria Celeste Galilei, Mary Allan-Olney

Galileo's Telescope and Celestial Discoveries

I am at present staying at Venice for the purpose of getting printed some observations which I have been making on the celestial bodies by means of a telescope which I have and being infinitely amazed thereat so do I give infinite thanks to God who has been pleased to make me the first observer of marvelous things unrevealed to by gone ages. I had already ascertained that the moon was a body most similar to the earth and had shown our Most Serene master as much but imperfectly not having such an excellent telescope as I now possess which besides showing me the moon has revealed to me a multitude of fixed stars never yet seen being more than ten times the number of those that can be seen with the unassisted eye. Moreover I have ascertained what has always been a matter of controversy among philosophers namely the nature of the Milky Way. But the greatest marvel of all is the discovery I have made of four new planets. I have observed their proper motions in relation to themselves and to each other and wherein they differ from all the other motions of the other stars. And these new planets move round another very great star in the same way as Venus and Mercury and peradventure the other known planets move round the Sun. As soon as my tract is printed which as an advertisement I intend sending to all philosophers and mathematicians. I shall send a copy to the Most Serene Grand Duke together with an excellent telescope which will enable him to judge for himself of the truth of these novelties.