ASTR 101 Lecture Notes - Lecture 20: Thirty Meter Telescope, Light Pollution, W. M. Keck Observatory
Telescopes allow us to collect and focus the light we need to derive the astrophysical understanding. Mainly to collect enough light to allow us to study extremely faint objects. Why are we interested in faint objects: some really interesting things are faint, even if nearby (like asteroids, rare objects, with special physics", tend to be very far away (since they are rare). Thus they look faint even if they are intrinsically quite bright: we want to study locations other than our own. How refracting telescope works: incoming light is focussed by an objective lens and then passed through an eyepiece lens to cast an image into your eye. Role of the eyepiece: objective lens turns image upside down, then the eye piece acts as a small magnifying glass, so what we see is a large inverted image. Magnification = focal length of objective/focal length of eyepiece. So you can get any magnification you want.