Optical astronomy

Visible-light astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light (optical telescopes). It includes imaging, where a picture of some sort is made of the object; photometry, where the amount of light coming from an object is measured, spectroscopy, where the distribution of that light with respect to its wavelength is measured, and polarimetry where the polarisation state of that light is measured. An example of spectroscopy is the study of spectral lines to understand of what kind of matter light is going through. Visible astronomy also includes looking up at night (). Visible-light astronomy is part of optical astronomy, and 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.