ASTR 101 Chapter Notes -Secondary Mirror, Consensus Cds Project, Chromatic Aberration
Telescopes: early telescopes first importantly used by galileo were refractor telescopes which use a glass lens to focus light of distant objects to a point. A big objective lens sits at the front of the telescope where its diameter determines how much light is collected. An eyepiece magnifies the focused image however nowadays most telescopes are fitted with special instruments or cameras to analyze the data. Telescopes gather light: magnification makes little difference when observing stars as they are too far away. Telescopes are useful because they capture the light and focus light from faint/dim objects. Most important dimension of the telescope is the diameter. Larger diameter = more light (which is why pupils dilate in the dark) Light-gathering power of a telescope is directly related to the size of the objective lens (location of light gathering) The area of the objective lens is related to the square of the diameter.