Optical astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light. 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.

Optical astronomy also includes looking up at night.