The image therefore becomes distorted.
Unwanted Refraction: pouring molten glass into a mold makes lenses. Air bubbles form in the lens as the liquid gas cools. The air bubbles cause, distorted images due to extra refractions.
Opaque: when some wavelengths of light can't pass through the lens, visible light is dimmed when it passes through, and the lens absorbs ultraviolet radiation.
The reflecting telescope was helpful in solving some of these problems because they use mirrors with top coated surfaces which light does not enter. Mirrors don't sag because they can easily be supported unlike heavy lenses. Since light doesn't enter the mirror, the problems of different wavelengths, chromatic aberration and opaque do not occur. However, spherical aberration can still occur because when light enters a telescope with a spherical mirror at different distances from the mirror's center, the light comes into focus at different focal lengths. One other main problem with reflecting telescopes is that they block out about ten percent of light attracted by the primary mirror. They are still the preferred telescopes to use. (B) I would build a reflecting telescope. I would want the mirror to be F/15, 800" at the most. Anything larger would not useless. I would ground, polish, shape and coat the mirror with aluminum coating. I would make the mirror concave in order to collect light to a point and then reflect it to a secondary mirror. I would turn the secondary mirror to a 45-degree angle and would build the eyepiece onto the side so that the light will come out the side.
3 #) Four telescopic discoveries made by Galileo were: 1) Venus goes through phases similar to those of the moon. This is significant because it proved that Venus goes around the sun, supporting the heliocentric cosmogony theory. 2) Galileo discovered four moons near Jupiter, which orbit Jupiter because they move back and forth from one side of the planet to the other.
