The atmosphere absorbs some light before it can reach a telescope’s detector, making objects appear fainter. the exact amount of absorption depends on the wavelength of light being observed, as shown in this graph of the percentage of light that can make it through the atmosphere to the ground. 0% transparency (atmosphere is opaque) means no light gets through, and 100% transparency means all the light gets through. the type of light per wavelength is labeled at the bottom of the figure. visible light is marked by the rainbow.