Refracting Uses lenses to bend light to a focal point Lightpath USNO 26 inch refracting telescope Reflecting Uses primary and secondary mirrors to reflect light into a focused area. Diagram Mirror configurations Newtonian . Elginfield Observatory in Ontario Advantages over refracting The amount of bending light experiences in a lense depends on wavelength. Mirrors are very efficient.
Lenses are heavy and can only be supported around edges.
If they get too big, they warp and distort the image. Mirrors can be supported over entire back surface. A mirror only needs one precision surface. A lense has 2. Lenses are formed by pouring molten glass into a mold and then polishing.