Reflecting Telescopes, such as the 200-inch on Mt. Palomar and the Hubble Space Telescope, use precisely curved concave mirrors at the lower end to focus starlight. Size for size these mirrors are less costly to make than the lenses used at the front end of the more familiar spyglass-like “Refracting” telescope. In a given price range large optics on a better mount are yours when you choose a reflecting telescopes. Never is this more true than when you compare telescopes available for under $300.00!
Larger diameter concave mirrors collect more starlight and make brighter, more detailed views of sky objects. Compared to common 60 mm refractors a 3-inch (76 mm) telescope makes stars appear 60% brighter!
4 1/4-inch telescope makes stars appear 3 1/4 times brighter than they appear in a 60 mm refractor. This increased brightness translates into a greater ability to reveal faint galaxies and nebulea.
REFRACTING TELESCOPE ……………NEWTONIAN REFLECTING SCOPE
a) Objective Lens ………………..a) Primary Mirror (Objective) b) Eyepiece………………………..b) Diagonal (Secondary) Mirror
c) Rays of light from a star ……c) Eyepiece
d) Focal Plane ……………………d) Focal Plane (at side of main tube)