Refracting telescope focus, results in a non-inverted and upright image. Galileo’s best telescope magnified objects about 30 times. Because of flaws in its design, such as the shape of the lens and the narrow field of view, the images were blurry and distorted. Despite these flaws, the telescope was still good enough for Galileo to explore the sky. The Galilean telescope could view the phases of Venus, and was able to see craters on the Moon and four moons orbiting Jupiter. Parallel rays of light from a distant object (y) would be brought to a focus in the focal plane of the
Craters of the Moon (geothermal site) of the Moon are the result of hydrothermal eruptions. The pressure of the steam beneath the surface exceeds the pressure exerted by the weight of the overlying ground. This results in an explosion. A mixture of hot water, steam, hot mud and pumice is ejected into the air. Material may be blown up to 100 m, leaving behind holes or craters as deep as 20 m. Hydrothermal eruptions occur about once a year. The openings in the earth surface, where geothermal steam and gases are emitted, are called fumaroles. These vary in size from one centimetre to half a meter