Visible-light astronomy
Visible-light astronomy encompasses a wide variety of astronomical observation via telescopes that are sensitive in the range of visible light (optical telescopes). Visible-light astronomy or optical astronomy differs from astronomies based on invisible types of light in the electromagnetic radiation spectrum, such as radio waves, infrared waves, ultraviolet waves, X-ray waves and gamma-ray waves. Visible light ranges from 380 to 750 nanometers in wavelength.
Visible-light astronomy has existed as long as people have been looking up at the night sky, although it has since improved in its observational capabilities since the invention of the telescope. This is commonly credited to Hans Lippershey, a German-Dutch spectacle-maker, although Galileo Galilei played a large role in the development and creation of telescopes.
Since visible-light astronomy is restricted to only visible light, no equipment is necessary for simply star gazing. This makes it the most commonly participated in type of astronomy, as well as the oldest.